Oracle case when then else end的两种用法

查询表结构

　　

SELECT 
       T.COLUMN_ID,
       T.COLUMN_NAME,
       (CASE
         WHEN (T.DATA_TYPE = 'VARCHAR2' OR T.DATA_TYPE = 'RAW') THEN
          T.DATA_TYPE || '(' || T.DATA_LENGTH || ')'
         WHEN (T.DATA_TYPE = 'NUMBER' AND T.DATA_PRECISION IS NOT NULL) THEN
          T.DATA_TYPE || '(' || T.DATA_PRECISION || ',' || T.DATA_SCALE || ')'
         ELSE
          T.DATA_TYPE
       END) AS DATA_TYPE,
       B.COMMENTS
  FROM USER_TAB_COLUMNS T
 INNER JOIN ALL_COL_COMMENTS B
    ON B.COLUMN_NAME = T.COLUMN_NAME
   AND T.TABLE_NAME = B.TABLE_NAME
   AND T.TABLE_NAME = 'T_WEIXIN_REMIND_FUND_CHANGE'
 ORDER BY T.COLUMN_ID;

　　第二种：红色部分可以把 T.DATA_TYPE 字段移动到CASE，WHEN 之间，这样when之后就直接写DATA_TYPE对应的值即可