PostgreSQL是一种开源的关系型数据库管理系统(RDBMS),它支持广泛的标准SQL语言,并提供了丰富的功能和扩展性。在PostgreSQL中,CASE/WHEN是一种条件表达式,用于根据给定的...
PostgreSQL的case when select tt.dict_labelas display_item,t1.ratiofrom (select t.product_level,round(sum(case when t.detect_result='2'then1else0end)::NUMERIC/count(1)::NUMERIC,4)as ratio from t_detect_record t where t.district='3'and t.e_commerce_platform='3' group by t.product_l...
条件 case s.××× when 'A' then (case when S.×× is null then '' else '' end) when 'B' then( case when S.×× is null then '' else '' end) when 'C' then( case when S.×× is null then '' else '' end) else s.order_class end 字符串连接以及截取某段字符串 table...
select COALESCE(null,null); //报错 select COALESCE(null,null,now()::varchar,''); //结果会得到当前的时间 select COALESCE(null,null,'',now()::varchar); //结果会得到'' //可以和其他函数配合来实现一些复杂点的功能:查询学生姓名,如果学生名字为null或''则显示“姓名为空” select case when coal...
postgre中没有类似的函数,可以重写为case... when... substr(str, int, int) Oracle中的substr用来取一个字符串的子串,PostgreSQL有同名的函数实现类似功能。不同的是Oracle中,第二、第三个参数可以为负数,代表从后面进行计数,PostgreSQL不允许其为负数,需对其进行转换。Oracle中是以0开始计数,PostgreSQL以1开始计...
(SELECTCASEWHENCOUNT((SELECTpg_sleep(20)))<>0THENtrueELSEfalseEND);-- - HAVING 如果parameter是整数: (COUNT((SELECTpg_sleep(20)))=1);-- - 如果parameter是字符串: t' AND (SELECT COUNT((SELECT pg_sleep(20))) = 1; -- - OFFSET...
However, databases don’t just store character strings: they also compare them, build indexes on them, change them to upper case, do regex searches on them, and other things that mean they need know what the characters are and how to manipulate them. So, PostgreSQL needs to know what char...
CASE deptype WHEN 'p' THEN 'pinned' WHEN 'i' THEN 'internal' WHEN 'a' THEN 'automatic' WHEN 'n' THEN 'normal' END AS "dependency type" FROM pg_catalog.pg_depend WHERE (objid >= 16384 OR refobjid >= 16384); 我通常喜欢在 where 后面加个条件and deptype <>'i',以排除 internal 依...
# we might not have a valid PostgreSQL connection here if another thread # stops PostgreSQL, therefore, we only reload replication slots if no # asynchronous processes are running (should be always the case for the master) if not self._async_executor.busy and not self.state_handler.is_starti...
UPDATE edge_table SET the_geom = st_makeline(st_point(x1,y1),st_point(x2,y2)), dir = CASE WHEN (cost>0 AND reverse_cost>0) THEN 'B' -- both ways,双向通行 WHEN (cost>0 AND reverse_cost<0) THEN 'FT' -- direction of the LINESSTRING,沿路通行 WHEN (cost<0 AND reverse_cost...