这是我的主查询中的查询。
SELECT
count(IF(source='L',1,NULL)) as L,
count(IF(source='B',1,NULL)) as B,
count(IF(source='M',1,NULL)) as M
FROM table_name WHERE tax_idno=main_query_id
除此之外还有更快的子查询吗?请帮忙,谢谢。
您可以使用 sum 函数代替 count 来优化查询:
SELECT
SUM(source='L') as L,
SUM(source='B') as B,
SUM(source='M') as M
FROM table_name
WHERE tax_idno=main_query_id;
并确保您对“source”和“tax_idno”有正确的索引