Vol. I · A Postgres HandbookTwelve chapters · · 756 queries

The Query & the Schema

A reading-room reference for writing PostgreSQL by hand — selects to window functions, with the schema in plain view.

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Chapters · Basic SELECT · Query 053 / 136
AdvancedBasic SELECT

Add a CHECK constraint

The query

SQL
ALTER TABLE employees 
ADD CONSTRAINT check_salary_positive 
CHECK (salary > 0);
Tested against PostgreSQL 16

Note

“Ensures custom business logic at the database level. Any insert/update violating this will fail.

Tables referenced

  • employees10 cols

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Multi-column UNIQUE constraint

The Query & the Schema

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Compiled for Postgres 16 · MMXXVI