如何为IF EXISTS指定列名

It's kind hard to explain, but I'm looking for replace this with IF EXISTS to improve performance:

这很难解释,但我正在寻找用IF EXISTS替换它以提高性能:

Select ... ,
     IF((SELECT COUNT( t.tab_id ) FROM tabs t WHERE t.marker_id = m.marker_id)>0,1,0) multimedia, ....
FROM markers m
WHERE ....

On this query, I would like to have a temporary column called "multimedia" filled by 1 if theres multimedia or 0 if there's not.

在这个查询中,我希望有一个名为“multimedia”的临时列,如果是多媒体则填充为1,如果没有,则填充0。

This code is executed by PHP...

这段代码由PHP执行......

1 个解决方案

SELECT 
  CASE 
    WHEN Exists(Select 1 FROM tabs t WHERE t.marker_id = m.marker_id)
      THEN 1
    ELSE 0
  END multimedia,
  ...

SELECT 
  CASE 
    WHEN Exists(Select 1 FROM tabs t WHERE t.marker_id = m.marker_id)
      THEN 1
    ELSE 0
  END multimedia,
  ...