select first_name || '.' || last_name, case when box1 is not null then box1 when box2 is not null then box2 when box3 is not null then box3 end as guess_what, date_time from guess_what; a 那么除了上面的两种使用的情况,COALESCE 还可以针对某些字段的类型进行转换,如日期类型转换为...
所以最好将空值null处理成0; 有两种方法,其实都是用条件表达式。 Case when Postgresql中条件表达式大家用 Case when用的很多,可以判断,将一列转多类数据转换成多列数据。 sum( CASE WHEN t2.refundamount1 IS NULL THEN 0::numeric ELSE t2.refundamount1 END) AS refundamount1 2.coalesce 函数 coalesce...
假设postgreSQL中表名为user,现在需要计算每个用户参加过的次数(is_join字段为null时不算,表中的null并不是字符串''或者字符串'Null' ,而是数据库中的null类型) 所以我们只需要对name分组并计算join_time不为null的个数,sql语句如下 SELECTname,SUM(CASEWHENis_joinisnullTHEN0ELSE1END)AScountFROM"user"GROUPBYn...
if 比较式 then begin end; end if; create or replace procedure test(x in number) is begin ifx >0 then begin x := 0 - x; end; end if; ifx = 0 then begin x: = 1; end; end if; end test; 2、For 循环 For ... in ... LOOP -- 执行语句 end LOOP; (1) 循环遍历游标 creat...
IF-THEN-ELSE语句在IF-THEN增加了条件表达式为false时,执行ELSE部分的脚本。例如: IF i_name is not null THEN select account into r_account from t_user t where = i_name ; ELSE raise notice '用户名为空'; END IF; 1. 2. 3. 4.
pg_table_is_visible(c.oid) ORDER BY 1, 2) LOOP IF obj.relhaspkey THEN PERFORM pglogical.replication_set_add_table(set_name := 'default', relation := obj.relname :: regclass); ELSE PERFORM pglogical.replication_set_add_table(set_name := 'default_insert_only', relation := obj.relname...
如上,我们插入4条数据,一个NULL,一个空字符串,一个空格字符串和包含一个字符的字符串.下面我们看看在Oracle中的处理: SELECT id, content, CASE WHEN content IS NULL THEN 1 ELSE 0 END AS isnull, CASE WHEN content = '' THEN 1 ELSE 0 END AS isempty, ...
SELECTemp_bonus,CASEWHENemp_bonusISNULLTHEN0ELSEemp_bonusENDASmodified_emp_bonusFROMemp_details; The output authenticates the working of CASE Expression. Conclusion SQL server offers an inbuilt function named ISNULL that is used to replace the NULL values with some specific values. However, Postgr...
优化版:SELECTt1.s_id,t1.s_name,count(t1.s_id),sum(casewhent2.scoreisNULLthen0elset2.scoreend)FROMstudentASt1LEFTJOINscoreast2ONt1.s_id=t2.s_idGROUPBYt1.s_id,t1.s_name 注意:这和代码有bug。王菊同学的选课数目应该为0 一个冗长的答案: ...
'||case when datname is null then 'NULL' else datname::text end||' , Client_Addr: '||case when client_addr is null then 'NULL' else client_addr::text end||' , Client_Port: '||case when client_port is null then 'NULL' else client_port::text end||' , Application_Name: '|...