oracle表列约束

1. 查看某张表列的约束及类型

SELECT   USER_CONS_COLUMNS.CONSTRAINT_NAME AS 约束名,   USER_CONS_COLUMNS.TABLE_NAME AS 表名,   USER_CONS_COLUMNS.COLUMN_NAME AS 列名,   CASE WHEN CONSTRAINT_TYPE='P' THEN '主键'       WHEN CONSTRAINT_TYPE='R' THEN '外键'       WHEN CONSTRAINT_TYPE='U' THEN '唯一约束'       WHEN CONSTRAINT_TYPE='C' THEN '检查约束'  END AS 约束类型,  USER_CONS_COLUMNS.POSITION AS 位置FROM   USER_CONSTRAINTS     JOIN USER_CONS_COLUMNS    ON (USER_CONSTRAINTS.CONSTRAINT_NAME         = USER_CONS_COLUMNS.CONSTRAINT_NAME) WHERE   USER_CONSTRAINTS.TABLE_NAME = '';