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 = '';