SELECT
tc.constraint_name, tc.table_name, kcu.column_name,
ccu.table_name AS foreign_table_name,
ccu.column_name AS foreign_column_name,
tc.is_deferrable,tc.initially_deferred
FROM
information_schema.table_constraints AS tc
JOIN information_schema.key_column_usage AS kcu ON tc.constraint_name = kcu.constraint_name
JOIN information_schema.constraint_column_usage AS ccu ON ccu.constraint_name = tc.constraint_name
WHERE constraint_type = ‘XXXXX‘ AND tc.table_name = ‘XXXXX‘;
constraint_type有四种：UNIQUE、PRIMARY KEY、CHECK、FOREIGN KEY
pgsql 查看表的约束情况
原文：https://blog.51cto.com/2012ivan/2522139
