So above sample data would satisfy the check constraint as there are following key value pair exists in phone_info column. So I want the my_text column to contain only 'A', 'B' or 'C' as values. In this case the data type is tsrange (short for “timestamp range Note. . Range types are data types representing a range of values of some element type (called the range's subtype ). The SQL Server documentation reflects the fact that the product only supports CHECK constraints at two physical levels, referred to as 'column' and 'table' but logically are column-level and row-level respectively. 179k 27 27 gold Jul 31, 2023 · Option 1: Change Property Name Convention. 2; check-constraints; Share. oid = con. Thankfully, PostgreSQL provides a way to list all constraints for a particular table. Given an existing Postgres DOMAIN with CHECK constraint: CREATE DOMAIN code as CHAR(1) CHECK (value IN ('A', 'B', 'C')); I need to alter the CHECK constraint to add D as a member to the valid set A, B and C. constraint_table_usage. You can add a new constraint with with alter table command. It allows us to verify a condition that the value being stored into a record. You could add a CHECK CONSTRAINT: ALTER TABLE distributors. Constraints on Ranges. The CHECK constraint is used to limit the value range that can be placed in a column. To ensure that a column does not contain null values Apr 28, 2022 · Table: create table tempchkconstraint ( colcode varchar, colname varchar, lastmoddate timestamp without time zone ); Need to validate the column 'colcode' if any data with character '-' is Jul 19, 2019 · 11. Then you can work with foreign keys instead of the check contraint. answered Feb 12, 2015 at 15:27. Option 4: Using HasCheckConstraint with Quoted Property Name. Every column constraint is equivalent to some table constraint. Jul 20, 2020 · Here is a simple way of getting all constraints of a table in PostgreSQL. If the values pass the check, PostgreSQL allows the insertion or update of those values into the column. Quote from the PostgreSQL manual: It should be noted that a check constraint is satisfied if the check expression evaluates to true or the null value. WHERE table_name = 'your_table'. A check constraint uses a boolean expression to evaluate the values, ensuring that only valid data Jun 12, 2012 · You can put an IS NULL test into the CHECK expression, like this: name TEXT, x INTEGER, y INTEGER CHECK (y IS NULL OR y > x) (tested on PostgreSQL 8. INNER JOIN pg_catalog. Alter table public. The documentation CHECK. MySQL Check Constraint for email Query below lists check constraints defined in the database ordered by constraint name. This assumption is what justifies examining CHECK constraints only when rows are inserted or updated, and not at other times. NOT NULL and CHECK constraints are not deferrable. superuser = True. 53. The foreign key defines a relationship between the two tables and enforces referential integrity in PostgreSQL. Tim Biegeleisen. Create a boolean function using the aggregate function bool_and() and use it as check expression: create or replace function check_bar_json(val jsonb) Apr 7, 2015 · According to the documentation, It should be noted that a check constraint is satisfied if the check expression evaluates to true or the null value. Try to find your constraint in this query result. A subquery is also known as an inner query or nested query. Sep 28, 2017 · I tried to insert some data in a database with postgresql but still showing the same message: ERROR: new row for relation "empleados" violates check constraint "ck_empleados_documento" DETAIL: Aug 8, 2014 · The standard names for indexes in PostgreSQL are: {tablename}_{columnname(s)}_{suffix} where the suffix is one of the following: pkey for a Primary Key constraint; key for a Unique constraint; excl for an Exclusion constraint; idx for any other kind of index; fkey for a Foreign key; check for a Check constraint; Standard suffix for sequences is create table user_has_job ( user_id integer references "user"(id), job_id integer references job(id), constraint user_has_job_pk PRIMARY KEY (user_id, job_id) ); But I want to create a check constraint that the user_id references a user that has user. SQL CHECK Constraint. I have checked the documentation provided by Oracle and found a way to modify a constraint without dropping the table. See full list on sqlshack. If the data fails the check, the operation is aborted, thus maintaining the integrity of your database. Here is how I want to implement it: create table words_table ( id serial primary key, words varchar(20)[] CHECK (array_length(words, 1) > 0) ); But looks like it doesn't work. 17. A foreign key establishes a link between the data in two tables by referencing the primary key or a unique constraint of the referenced table. Aug 14, 2020 · So, here you should use Trigger on BEFORE INSERT event of your Votes Table or you can use function/procedure(depend upon your version of PostgreSQL) for your insert operation where you can check the value before insert and raise exception if the condition not satisfied. FROM information_schema. table_schema as table_schema, ccu. So changing the constraint to ab>=h works for that specific query (actually it is more correct for the problem) but is there a way Jul 18, 2020 · The documentation seems to imply that the NOT VALID option is mostly for performance reasons, to allow the user to defer the validation until later. Alternatively you can use pg_constraint to retrieve this information. Use the fields in the Definition tab to define the check constraint: Provide alter table node_access add constraint block_anonymous_page_edit. The basic syntax of the subquery is as follows: select_list. c = check constraint f = foreign key constraint p = primary key constraint u = unique constraint t = constraint trigger x = exclusion constraint From a software developer point of view, I have a slight preference for using check constraints, since PostgreSQL enum's require a cast in your SQL to do an update/insert, such as: INSERT INTO table1 (colA, colB) VALUES('foo', 'bar'::myenum) where "myenum" is the enum type you specified in PostgreSQL. Nov 19, 2013 at 20:22. A not-null constraint is always written as a column constraint. That cannot be a list that changes based on what is in the database or something else that is not immutable. alter table my_table. The table containing a foreign key is referred to as the referencing table or With PostgreSQL 9. a = NULL. They allow you to define rules that data in a specific column must Jan 26, 2017 · 4 Tables:\. An idea is to allow only arrays with length > 0. Improve this question. relname as table_name, c. char_length(foo) <= 255. It can refer to a single column, or multiple columns of the table. ON nsp. conname as constraint_name, ccu. Store notes about the check constraint in the Comment field. In PostgreSQL, the Check constraint can be defined by a separate name. ,''"]') Apr 16, 2011 · PostgreSQL check constraint. Whenever a row is inserted or updated, the constraint checks the validity of the input data against the defined condition. The view check_constraints contains all check constraints, either defined on a table or on a domain, that are owned by a currently enabled role. This gives varchar(N) a clear advantage, as increasing N is basically instantaneous, while changing the CHECK constraint on a text field will involve re-checking the entire table. Practical examples with the tv_series table included. x: CREATE UNIQUE INDEX constraint_name ON table_name (columns); Mar 9, 1998 · You could also use a case insensitive regex in Postgres, and tighten up to this: CONSTRAINT proper_nccondutor CHECK (nccondutor ~* '^[a-z]{2}-[0-9]{7}$') The above assumes that you intend the pattern to be a full match, which seems to be the case. Let’s create a table named ‘furniture’ to understand the example using the CREATE TABLE statement as follows: Now try to insert negative furniture prices into the furniture table. Introduction to PostgreSQL CHECK constraints. ERROR: new row violates check option for view "fte" DETAIL: Failing row contains (24, Peter, Taylor, 1, Contractor). check_constraints. Jul 12, 2018 · Conditional check constraint in Postgresql with Regex. Apr 5, 2012 · Postgres Check Constraint definition. CHECK (Column_Name !~ '[. Feb 10, 2015 · Normally I would just add a fk constraint on b. For instance, ranges of timestamp might be used to represent the ranges of time that a meeting room is reserved. contype = 'f') then kcu. id). Check this query to see them organized by table. id_a" to reference the fk on b. e: Only those routines are shown that are owned by a currently enabled role. check (grant_update = 0 WHERE (gid = 1 AND realm = 'nodeaccess_rid')); This is supposed to make sure that grant_update is equal to 0 when gid is 1 and realm = nodeaccess_rid. pg_constraint. This will disable that constraint. The constraint must be a predicate. table_schema as table_schema, kcu. 9. The problem is that I'm not allowed to add a pk or uq constraint to "a. table_constraints WHERE table_name='my_table' AND constraint_type='UNIQUE'; Note that a column can have multiple constraints such as NOT NULL, check, unique, foreign key appearing next to each other. Hope this works. Query select pgc. To drop a constraint, you will use the ALTER TABLE command followed by DROP CONSTRAINT, and then specify the name of the constraint. SELECT constraint_name, table_name, column_name, ordinal_position FROM information_schema. You need to retrieve the table names by running the following query: SELECT *. O_o postgresql-9. However, I think rather than doing what I want, it's actually trying to make all columns mimic these values. I understand I can use the following to only allow alphanumeric characters but I need to be able to accept the other special characters as well. 5 forward, when a table has multiple check constraints, they will be tested for each row in alphabetical order by name and after NOT NULL constraints. Each time you insert or update a record, PostgreSQL checks these conditions. Check constraints are an essential aspect of maintaining data integrity in a PostgreSQL database. It must be int (the underlying type of users. Sep 23, 2023 · Navigate the world of PostgreSQL Constraints with this overview guide. To get a list of all constraint names associated with a table, you can run the following SQL query: SELECT conname AS constraint_name FROM pg_constraint INNER JOIN pg_class ON conrelid=pg_class. Problem is, it errors out at modify as it does not recognize the keyword. Check constraint is a constraint that allows specifying the conditions that the values of columns Nov 29, 2022 · Is there a possibility to add a check constraint to ensure the length of the elements in a text[] in postgres? I want each element to have a length of 2 characters (country iso code). Check constraints will apply to a single row in a table. Among these is the CHECK constraint, which ensures that all values in a column satisfy a specific condition. You can do what you want with MATCH FULL. PostgreSQL does not support CHECK constraints that reference table data other than the new or updated row being checked. For example, in our schema we need to add some logic to our reservations times. Does it matter if a constraint is not marked as valid forever? postgresql. contype = 'f') then ccu. If the condition returns true, the operation proceeds; if false, the Oct 26, 2019 · 5. And then update ' conrelid ' to 0 for that entry. Here is the how to add a unique constraint to your table in PostgreSQL 9. consrc as definition from pg_constraint pgc join pg_namespace nsp on nsp. To enforce the listed combinations, your table definition could look like this: CREATE TABLE jobs. Constraints allow developers to specify rules and restrictions for the Aug 12, 2021 · A CHECK constraint does the job. The order of the constraints is not important. This page explains how to configure check constraints in a PostgreSQL database. Jun 18, 2024 · On PostgreSQL, there’s a native BOOLEAN type, so the CHECK constraint of Boolean is not needed; we are safe to set up a Boolean type without a name, even though a naming convention is in place for check constraints. You can do like this. (column_1 IS NULL) != (column_2 IS NULL)); (But the above approach is not generalizable to three or more columns. May 24, 2023 · Examples. ) Not-null constraints are represented in the pg_attribute catalog, not here. contype as constraint_type, ccu. While a CHECK constraint that violates this rule may appear to work in simple tests, it cannot guarantee that the database will not reach a state in which the constraint condition is false (due to subsequent changes of the other row(s) involved). EDIT: After some digging I have tried this. Jun 1, 2020 · The CHECK constraint utilizes a Boolean expression to assess the values before performing an insert or update operation to the column. column_name else ccu. Ordinarily this is checked during the ALTER TABLE by scanning the entire table; however, if a valid CHECK constraint is found which proves no NULL can exist, then the table scan is skipped. 1, the NOT VALID modifier was only available for FK constraints. Your two options are change your constraint to ab>=h or remove/update the rows that are violating the original cosntraint. The drawback is that you cannot give explicit names to not-null constraints created this way. mu is too short. PostgreSQL CHECK constraint with the default name. table_name else (null) end as reference Apr 21, 2016 · The only argument against varchar(N) was that changing N required a table rewrite, and as of Postgres 9. connamespace join pg_class cls on pgc. The manual: If the constraint is marked NOT VALID, the potentially-lengthy initial check to verify that all rows in the table satisfy the constraint is skipped. Postgres does not attempt to simplify your expression. For example, the following PostgreSQL statement creates a new table called COMPANY5 and adds five columns. check_constraints Columns. 37. Jan 4, 2024 · A CHECK constraint is a rule that specifies the acceptable data values that can be held by a column or a combination of columns in a PostgreSQL table. Sep 15, 2021 · 1. nspname as schema_name, t. WHERE nsp. PostgreSQL - Multiple constraints. ) Table 37. Usecase: it's a filter. If you define a CHECK constraint on a column it will allow only certain values for this column. lator. (The owner of the table or domain is the owner of the constraint. Name of the schema containing the constraint. oid Feb 13, 2015 · 2. Follow edited Feb 3, 2016 at 15:53. alter table table_1. Because this handy little feature check constraints allows you the same functionality in Postgres with even more flexibility. CHECK (element_type = 'lesson' OR element_type = 'quiz'); Although IMO the cleaner option would be to create an ENUM: CREATE TYPE element_type AS ENUM ('lesson', 'quiz'); edited Aug 31, 2011 at 1:29. Click the Definition tab to continue. pg_namespace nsp. If you use NULL instead of NOT NULL, the column will accept both NULL and non-NULL values. I would like to add a constraint to a column that is of Character datatype to have only 3 allowed values: id character varying(255) NOT NULL, uid character varying(255) NOT NULL, my_text text NOT NULL, is_enabled boolean NOT NULL. add constraint number_must_have_value CHECK (attribute = 't' and number IS NOT NULL) It throw constraint is violated by some row, but if I run: select * from my_table where attribute = 't' and Jun 16, 2021 · 1 Answer. The result of the predicate can be either TRUE, FALSE, or UNKNOWN, depending on the presence of NULLs. Erwin Brandstetter. It's your responsibility to provide sensible expressions. 8. table_name as table_name, case when (pgc. A not-null constraint is functionally equivalent to creating a check constraint CHECK (column_name IS NOT NULL), but in PostgreSQL creating an explicit not-null constraint is more efficient. users_id is text. 7. a != NULL. g. demo:db<>fiddle. ADD CONSTRAINT check_types. Sorted by: 3. Sep 23, 2023 · The CHECK constraint in PostgreSQL allows you to define one or more conditions that the data in a table must satisfy. It will retrieve all columns and their relationship as well: select *FROM ( from ( select pgc. Jan 5, 2024 · Dropping Constraints: The Basics. Another difference is that constraint exclusion is only applied at plan Here is an elegant two column solution according to the "constraint -- one or the other column not null" PostgreSQL message board: ALTER TABLE my_table ADD CONSTRAINT my_constraint CHECK (. main. Think of it like a generalised UNIQUE constraint: instead of "no two rows can be equal", you can say things like "no two rows overlap", or even "no two rows can be different". constraint_column_usage where table_name = t_name and constraint_name = c_name) then execute constraint_sql; end Aug 19, 2017 · I'm playing with postgres table validation rules and trying to set a CHECK constraint for an array column. A check constraint allows you to enforce data integrity rules at the database level. Name of the database containing the constraint (always the current database) constraint_schema sql_identifier. If you define a CHECK constraint on a table it can limit the values in certain columns based on values in other columns in the row. answered Apr 21, 2016 at 22:05. This check helps maintain data integrity by preventing invalid data from being entered into the table. Apr 10, 2015 · The syntax for a check constraint is CONSTRAINT name CHECK (condition) (or just CHECK (condition) and Postgres itself will come up with a name) in a CREATE TABLE statement, and ALTER TABLE table_name ADD CONSTRAINT name CHECK (condition);. Would be nice if somebody has a solution for me. Using EMS SQL Manager for PostgreSQL. Edit: Why not fk constraint - My model consists of an ESRI Arc SDE with spatial tables and simple postgres tables. Jan 28, 2014 · Now I need to add a check constraint on phone_info column so that all key for "STATUS" ie(1010101010,2020202020) should exist as a (key,value) pair of phone_info column where value would be "OK". PostgreSQL regex to validate email addresses. edited Sep 18, 2021 at 11:08. You can logically have constraints at every level: (column, domain, row, table, schema, database, enterprise, global). It is primarily used while creating a table. Nov 19, 2020 · From the documentation: But the database will not assume that the constraint holds for all rows in the table, until it is validated by using the VALIDATE CONSTRAINT option. CHECK constraint to check substring matches other column (PostgreSQL) 3. Postgresql - Check constraint with conditions. com Jun 15, 2015 · I have a table definition in Postgres. Hot Network Questions Nov 17, 2015 · The function jsonb_object_keys(jsonb) returns set, while an expression in check cannot return set. I need to limit five special characters in my column specifically: period, comma, single-quotes, double-quotes, and dollar sign. c = NULL. conname as constraint_name. From documentation this example: ALTER TABLE distributors. In this post, the guy says : " You can even leave the constraint in a NOT VALID state, since May 2, 2013 · Checking of constraints that are deferrable can be postponed until the end of the transaction (using the SET CONSTRAINTS command). 0. This command complies with the behavior defined in the SQL standard, except for the limitation that, in PostgreSQL, it does not apply to NOT NULL and CHECK constraints. I would want to make a check constraint which basically follows the following logic: main. notIMMUTABLE. It is used to control the value of columns being inserted. This problem can appear when querying information schema views such as check_constraint_routine_usage , check_constraints , domain_constraints , and referential_constraints . oid = connamespace. There are good reasons for this restriction, but Oct 10, 2017 · 3. Syntax: variable_name Data-type CHECK(condition); Now let’s Sep 3, 2014 · Up to Postgres 9. #. Check constraint. Is that possible? Or is there another solution? Jan 17, 2022 · 184. 4) This is simply not necessary. condition would be an expression using an appropriate string function, e. Introduction to PostgreSQL subquery. It doesn't mention the consequences – not even in the notes –, if there are any at all. Jun 7, 2023 · The check constraint can be used to enforce rules on columns, such as limiting the values that can be entered in a particular column or ensuring that certain columns are always populated with valid data. In PostgreSQL, a foreign key is a column or a group of columns in a table that uniquely identifies a row in another table. 515k 29 306 381. answered Nov 19, 2022 at 16:02. Since the new constraint is a superset of the first it seemed acceptable to first DROP the existing constraint and then ADD it again; i. Start time should be less than the end time. select n. A subquery is a query nested within another query. Option 3: Manual Check Constraint SQL. id_a. oid = pgc. ) Oct 16, 2019 · ON rel. Code language: JavaScript (javascript) The WITH CASCADED CHECK OPTION instructs PostgreSQL to check the constraint on the fte_1 view and also its base view which is the fte view. (Column constraints are not treated specially. column_name end as column_name, case when (pgc. nspname = 'public' and contype='c'. Jul 9, 2018 · Whereas a CHECK constraint evaluates an expression based on a single row of the table, an EXCLUDE constraint evaluates a comparison of two rows in the table. . Table 37. FROM. Indexing. This was extended to CHECK constraints in Postgres 9. May 2, 2020 · PostgreSQL exposes the constraints as well as other schema details through information_schema, so to find all the constraints for the table, query table_constraints, for example: SELECT constraint_name FROM information_schema. Note. 2, this is no longer the case. public_insurer_credit MODIFY CONSTRAINT public_insurer_credit_fk1 deferrable, initially deferred; Yes, you can. If this table is a partition, one cannot perform DROP NOT NULL on a column if it is marked NOT NULL in the parent table. This convention will only be consulted for the CHECK constraint if we run against a database without a native BOOLEAN type like A check constraint that references another table like that is called a FOREIGN KEY. Apr 5, 2022 · Every boolean expression is valid for a CHECK constraint. Learn what constraints are, why they're important, and get introduced to different types of constraints like PRIMARY KEY, FOREIGN KEY, UNIQUE, and CHECK. Column Type. Since most expressions will evaluate to the null value if any operand is null, they will not prevent null values in the constrained columns. – onedaywhen. – Filipe Silva. If the statement is false, then the data disrupts the constraint which is not saved in the table. Feb 1, 2019 · Postgres Check Constraint definition. a Boolean (truth-value) expression. A subquery can be useful for retrieving data that will be used by the main query as a condition for further data selection. 1. So if enums are handy, then why in our internal chat was there little to no examples of them being actually used out in the wild. Aug 14, 2018 · Here is PostgreSQL specific answer. If the condition evaluates to false, the record violates the constraint and is not entered into the table. Feb 9, 2022 · Check constraints are a great way to add some simple logic to your data by having the database check something before an insert. Currently, only UNIQUE, PRIMARY KEY, EXCLUDE, and REFERENCES (foreign key) constraints accept this clause. To create a check constraint in PostgreSQL, you can use the following syntax: where table_name is the name of the table you want to add the 8. A check constraint is a type of integrity constraint in SQL which specifies a requirement that must be met by each row in a database table. Perhaps you can ask another question that describes your actual problem. 10. Jan 19, 2016 · I want to set a check constraint on the following postgres table: CREATE TABLE foo. key_column_usage WHERE table_name = '<your_table_name>'; edited Oct 5, 2023 at 10:17. 6. PostgreSQL assumes that CHECK constraints' conditions are immutable, that is, they will always give the same result for the same input row. Description. The constraint will still be enforced against Oct 15, 2021 · "Each part will be taken from a list": then you cannot use that in a check constraint, because you need to know that list when you create the constraint. But nowhere it says explicitly that it can not be used for the purpose of keeping old (invalid) data. Hot Network Questions Jan 6, 2024 · PostgreSQL, a powerful open-source object-relational database system, offers robust data validation mechanisms. id int Primary Key, names varchar(40)[] Since names is an array, I have trouble defining a check on each element of the array. conrelid. Data validation with CHECK constraints (PostgreSQL) Overview . NOT DEFERRABLE is the default. oid WHERE relname='table_name'; For that purpose, we will use the CHECK constraint as follows: ADD CONSTRAINT book_price CHECK (book_price <= 1000 ); Now, the book_price column will not accept those value that exceeds the book_price 1000: VALUES ( 'Introduction to Postgres', 'Database', '2008-06-01', 1500 ); The output shows that the value entered for the book_price column Apr 27, 2022 · In a normalized design you would deal with this requirement by creating 2 tables: one for all possible statuses and the other for the subtypes of the statuses and in the table person you would only have 1 foreign key referencing the subtype of the status. Aug 1, 2016 · So if a record is saved with attribute value 'true' then number must be given a value. Dec 8, 2022 · Check constraints. But if you have non-unique entries in your table, it will fail. 13. Constraint exclusion works in a very similar way to partition pruning, except that it uses each table's CHECK constraints — which gives it its name — whereas partition pruning uses the table's partition bounds, which exist only in the case of declarative partitioning. check_constraint_routine_usage Columns. As a special note the types must be the same, so in your example tasks. A check constraint is a condition that must be satisfied before a value can be saved to a table - for example, the discounted price of a product must always be less than the original price. 10. The following constraint is my best guess (not working) : ADD CONSTRAINT check_names. Option 2: Use Data Annotations. Example. Currently, CHECK expressions cannot contain subqueries nor refer to variables other than columns of the current row. 2. conrelid = cls. The CHECK Constraint enables a condition to check the value being entered into a record. Using the <@ operator: CHECK(scopes <@ ARRAY['read', 'write', 'delete', 'update']) Not knowing your exact use case, but I would prefer a more normalized solution: Putting the four operations into a separate table which can be updated. The catalog pg_constraint stores check, primary key, unique, foreign key, and exclusion constraints on tables and contype column saves data about the type of the constraint i,e. Here’s a basic example of how to remove a constraint named ‘user_email_key’ from a table called ‘users’: It’s important to know the exact name of the constraint. Let’s create table furniture to understand the CHECK constraint in detail. USING Trigger: CHECK Constraint. using postgres constraints for form validation. phase_steps ( phase_step_id integer GENERATED ALWAYS AS IDENTITY PRIMARY KEY , step_type text , step_status text , CONSTRAINT step_status_for_step_type CHECK ( step_type = 'RESEARCH' AND step_status IN ('COMPLETE A check constraint specified as a column constraint should reference that column's value only, while an expression appearing in a table constraint can reference multiple columns. – 144. A Foreign key is a column or group of columns in one table that references one or more columns from another table. Nov 19, 2013 · The constraint will be in place for all the rows. Note: PostgreSQL does not support CHECK constraints that reference table data other than the new or updated row being checked. table_name, ccu. Your try to cast jsonb_object_keys(jsonb)::text[] is incorrect, you need an aggregate. In PostgreSQL, a CHECK constraint ensures that values in a column or a group of columns meet a specific condition. constraint_catalog sql_identifier. Mar 18, 2019 · This might help, although it may be a bit of a dirty hack: create or replace function create_constraint_if_not_exists ( t_name text, c_name text, constraint_sql text ) returns void AS $$ begin -- Look for our constraint if not exists (select constraint_name from information_schema. PostgreSQL may check constraints in any order. main, which an id, a type variable (lets make it a smallint of 0-2), and foreign keys to the following tables: a, b, and c, which only contain an id. Also, PostgreSQL checks non-deferrable uniqueness constraints immediately, not at end of statement as the standard would suggest. The catalog pg_constraint stores check, primary key, unique, foreign key, and exclusion constraints on tables. PostgreSQL automatically-generated constraint names avoid duplicates in the same schema, but users can specify such duplicate names. column_name, pgc. SQL Query to Find Constraint Names. Simpler, cheaper and more reliable than a trigger. add constraint ck_only_one check ((col1 is null and col2 is not null) or (col2 is null and col1 is not null)); Separation with parenthesis is to be given for better segregation. b = NULL. ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5) NO INHERIT; You will have to replace constraint name as well as table name and content by your local requirements. by tw dg zd zu uh ai pk ow mm