Скачать или смотреть 17 | What is CHECK CONSTRAINT in SQL and How to use CHECK | Oracle PL/SQL Programming

Check constraints
A check constraint can be used to specify a wide range of rules for the contents of a table. A search condition (which is a boolean expression) is specified for a check constraint. This search condition must be satisfied for all rows in the table. The search condition is applied to each row that is modified on an INSERT or UPDATE at the time of the row modification. The entire statement is aborted if any check constraint is violated.

Requirements for search condition
If a check constraint is specified as part of a column-definition, a column reference can only be made to the same column. Check constraints specified as part of a table definition can have column references identifying columns previously defined in the CREATE TABLE statement.

The search condition must always return the same value if applied to the same values. Thus, it cannot contain any of the following:
Dynamic parameters (?)
Date/Time Functions (CURRENT_DATE, CURRENT_TIME, CURRENT_TIMESTAMP)
Subqueries
User Functions (such as USER, SESSION_USER, CURRENT_USER)
17 | What is CHECK CONSTRAINT in SQL and How to use CHECK | Oracle PL/SQL Programming

#check_constraint #oracle_pl_sql #sql_constraint #oracle_constraint