SQL 指定字段的值排序，CASE WHEN 使用

如下：

SELECT id, 
        (CASE WHEN category_type IN (1, 2, 7, 6, 9) THEN ( SELECT count(1) FROM agent_type_1 )
        ELSE ( SELECT count(1) FROM agent_type_2 ) END ) AS count
FROM product_category WHERE `status` = 2
ORDER BY FIELD(category_type, 3, 4, 8, 1, 2, 6, 7, 9), count DESC

Field函数可以帮我们做到！