原文:NULLIF expressions Use the NULLIF expressions for conditional expressions in Derby.NULLIF expression syntax NULLIF ( L, R ) The NULLIF expression is very similar to the CASE expression. For example: NULLIF(V1,V2) is equivalent to the following CASE expression: CASE WHEN V1=V2 THEN NULL ELSE V1 END
好象不对.看这句NULLIF(V1,V2) is equivalent to the following CASE expression: CASE WHEN V1=V2 THEN NULL ELSE V1 END
用CASE WHEN 去做吧.case when col is null then '指定值' else col end ;同样的效果.
java开源数据库啊,没用过
TRY
NULLIF(V1,V2)
Use the NULLIF expressions for conditional expressions in Derby.NULLIF expression syntax
NULLIF ( L, R )
The NULLIF expression is very similar to the CASE expression. For example:
NULLIF(V1,V2)
is equivalent to the following CASE expression:
CASE WHEN V1=V2 THEN NULL ELSE V1 END
is equivalent to the following CASE expression:
CASE WHEN V1=V2 THEN NULL ELSE V1 END