Postgresql like into if 子句

Question

我得到了这个 PostgreSQL 查询:

SELECT Sum(CASE 
                 WHEN p LIKE '%add%' 
                      AND p NOT LIKE '%add post%' THEN counter 
                 ELSE 0 
               end) AS "AGREGAR",
          Sum(IF p LIKE '%add%' AND p NOT LIKE '%add post%' THEN 1 ELSE 0 END IF ) AS P 
    FROM   (SELECT l.action AS p,
                   Count(l.userid) AS counter
                   --r.name 
            FROM   mdl_log AS l 
                   JOIN mdl_role_assignments AS ra 
                     ON l.userid = ra.userid 
                   JOIN mdl_role AS r 
                     ON ra.roleid = r.id 
                   JOIN mdl_course AS c 
                     ON c.id = l.course 
                        AND course = 12033 
                        AND roleid = 3 
            GROUP  BY roleid, 
                      l.action, 
                      r.name 
            ORDER  BY l.action) AS "P"

但是当我执行它时，我得到了这个错误:

ERROR:  error de sintaxis en o cerca de «p»
LINE 6:               Sum(IF p LIKE '%add%' AND p NOT LIKE '%add pos...
                             ^
********** Error **********

ERROR: error de sintaxis en o cerca de «p»
SQL state: 42601
Character: 216

这就像引擎无法识别子查询中的“p”别名，但是当我在选择中不再输入“p”时，它工作正常。我究竟做错了什么？

Answer 1

将带有 if 条件的行更改为普通的 case 表达式:

Sum(CASE WHEN p LIKE '%add%' AND p NOT LIKE '%add post%' THEN 1 ELSE 0 END) AS P 

你应该没问题。 if 语句用于函数和触发器等中使用的 PL/pgSQL 语言。