sql - 保留前 N 行并删除其余行

Question

尝试编写一个 sql 来保留表的前 N ​​行并删除其余行。我想出了这个 sql，但它说我不能在这里使用计数。请帮我重新编写sql。

DELETE 
  FROM ZZ_TEST_FINTABLE
 WHERE PROCESS_INSTANCE = ( 
 SELECT MIN(B.PROCESS_INSTANCE) 
  FROM ZZ_TEST_FINTABLE B) 
   AND COUNT(PROCESS_INTANCE) > 9

Answer 1

也许这对你有用（使用 Oracle DB）

DELETE FROM
    ZZ_TEST_FINTABLE 
WHERE
    PROCESS_INSTANCE NOT IN 
    (
        SELECT PROCESS_INSTANCE 
        FROM ZZ_TEST_FINTABLE 
        WHERE ROWNUM < 9
    );

Answer 2

您必须为您的表修改它，但应该可以：

DELETE FROM myschema.mytable WHERE pkey NOT IN (SELECT pkey FROM myschema.mytable ORDER BY pkey FETCH FIRST 10 ROWS ONLY)

Answer 3

您应该使用 HAVING 而不是 AND。

   DELETE 
   FROM ZZ_TEST_FINTABLE
   WHERE PROCESS_INSTANCE = ( 
                            SELECT MIN(B.PROCESS_INSTANCE) 
                             FROM ZZ_TEST_FINTABLE B
                            ) 
   HAVING COUNT(PROCESS_INTANCE) > 9

或这个

    DELETE 
    FROM ZZ_TEST_FINTABLE A
    INNER JOIN ZZ_TEST_FINTABLE B ON A.PROCESS_INSTANCE= MIN(B.PROCESS_INSTANCE)
    HAVING COUNT(PROCESS_INTANCE) > 9