加一行 NULL 即可例如:SQL> DECLARE 2 testvalue INT; 3 BEGIN 4 testvalue := 200; 5 6 IF testvalue > 100 THEN 7 8 ELSIF testvalue = 100 THEN 9 dbms_output.put_line( '100' ); 10 ELSE 11 dbms_output.put_line( '100-' ); 12 END IF; 13 14 END; 15 / ELSIF testvalue = 100...
SELECT product, (price - COALESCE(discount,0)) AS net_price FROM items; 1. 2. 返回结果: 现在D的净价为500,因为计算时使用0代替折扣null值。除了使用 coalesce 函数,我们也可以使用 case 表达式处理null值。请看示例: SELECT product, ( price - CASE WHEN discount IS NULL THEN 0 ELSE discount END ...
...可以使用 case when 子句进行条件判断,当「登出时间」这一列的某个值为空值时,则使用当天 23:59:59 作为值,否则就不改变值,即: case when 登出时间 is null then...当天23:59:59 else 登出时间 end 除了使用 case when 填充空值,还可以使用 ifnull() 函数填充空值。...合并字符串...
*/ if (bgwriter_lru_maxpages <= 0) { saved_info_valid = false; return true; } /* * Compute strategy_delta = how many buffers have been scanned by the * clock sweep since last time. If first time through, assume none. Then * see if we are still ahead of the clock sweep, and ...
SQL CASE表达式是一种通用的条件表达式,类似于其它语言中的if/else语句。 CASE WHEN condition THEN result [WHEN ...] [ELSE result] END condition是一个返回boolean的表达式。如果为真,那么CASE表达式的结果就是符合条件的result。如果结果为假,那么以相同方式搜寻随后的WHEN子句。如果没有WHEN condition为真,那么...
IFNOTEXISTS(SELECT1FROMmd_UserBotProjectASproWHEREpro.SchoolId=_schoolid)THENINSERTINTOmd_UserBotProjectSELECTProject.Id, _schoolid,NULLFROMProjectLEFTOUTERJOINmd_UserBotProjectON(md_UserBotProject.ProjectId=Project.Id);-- WHERE md_UserBotProject.ProjectId IS NULL;GETDIAGNOSTICS r_count :=row_cou...
[data, setData] = useState({email: null, password: null}); const router = useRouter() const submit = (e) => { e.preventDefault() if(data.email && data.password) { postData('/api/login', data).then(data => { console.log(data); if (data.status === "success...
(reln, forknum, blocknum, true /* not used */ , EXTENSION_DONT_OPEN); /* * We might be flushing buffers of already removed relations, that's * ok, just ignore that case. If the segment file wasn't open already * (ie from a recent mdwrite()), then we don't want to re-open...
问无法删除索引，因为唯一约束需要它(postgres)EN这两天在开发过程中，有个需求，就是找出某个schema的...
more because it's "not true", rather then false. But negating such an expression yieldsnull...