PostgreSQL查詢約束和創建刪除約束

查詢約束constraint

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 = 'UNIQUE' AND tc.table_name = 'table_name'; 

constraint_type有四種：UNIQUE、PRIMARY KEY、CHECK、FOREIGN KEY, 通過修改上邊sql語句的table_name和constraint_type來進行相應的查詢。

添加約束

ALTER TABLE table_name ADD CONSTRAINT uk_users_name1 UNIQUE (NAME);

刪除約束

alter table table_name drop constraint if EXISTS uk_users_name1;

約束內容可參考
鏈接: 約束內容.