ALTER TABLE ... ADD constraint

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Add a constraint to a table.

schema:scott

We can add a constraint

  • a foreign key reference
  • a UNIQUE requirement
  • a CHECK constraint

This is in the SQL standard <a href="http://sqlzoo.net/sql92.html#alter_table_statement">ALTER TABLE</a>

DROP TABLE a
CREATE TABLE a(x INTEGER, y INTEGER);
INSERT INTO a VALUES (1,2);
ALTER TABLE a ADD CHECK (y>0)
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