[GitHub] [incubator-doris] yangzhg opened a new pull request #3135: support subquery in case when statement

[GitBox]

yangzhg opened a new pull request #3135: support subquery in case when statement
URL: https://github.com/apache/incubator-doris/pull/3135
 
 
   implement subquery support for  sub query in case when statement like
   ```
   SELECT CASE
           WHEN (
               SELECT COUNT(*) / 2
               FROM t
           ) > k4 THEN (
               SELECT AVG(k4)
               FROM t
           )
           ELSE (
               SELECT SUM(k4)
               FROM t
           )
       END AS kk4
   FROM t;
   ```
   
   this statement will be rewrite to 
   ```
   SELECT CASE
           WHEN t1.a > k4 THEN t2.a
           ELSE t3.a
       END AS kk4
   FROM t, (
           SELECT COUNT(*) / 2 AS a
           FROM t
       ) t1,  (
           SELECT AVG(k4) AS a
           FROM t
       ) t2,  (
           SELECT SUM(k4) AS a
           FROM t
       ) t3;
   ```

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