如果条件在JOOQ的总和之内

Question

MySQL allows me to run the following query:

SELECT SUM(IF(COLUMN1 > COLUMN2, COLUMN2, COLUMN1)), SUM(IF(COLUMN3 = 0,4 ,10)) FROM TABLE;

How can I do this in JOOQ ?

Answer 1

I'm assuming you're referring to MySQL's IF() function, which is currently not supported by jOOQ, simply because if is a reserved keyword in Java, so there's no 1:1 mapping to a Java method for this function.

But as you can also see in MySQL's documentation, you can very easily rewrite IF() to the more standard CASE expression. So, your query would be this one in SQL:

SELECT 
  SUM (CASE WHEN COLUMN1 > COLUMN2 THEN COLUMN2 ELSE COLUMN1 END), 
  SUM (CASE WHEN COLUMN3 = 0 THEN 4 ELSE 10 END)
FROM TABLE

Which translates to jOOQ as follows:

using(configuration)
  .select(sum(when(TABLE.COLUMN1.gt(TABLE.COLUMN2), TABLE.COLUMN2)
             .otherwise(TABLE.COLUMN1)),
          sum(when(TABLE.COLUMN3.eq(0), 4).otherwise(10)))
  .from(TABLE)
  .fetch();

See the jOOQ manual's section about the CASE expression for details .

As always, this static import is implied:

import static org.jooq.impl.DSL.*;