Question

见下面的查询。我想获得子查询中返回的表的大小，但.size不起作用。有办法解决这个问题吗？

SELECT 
    (SELECT 
        ROUND(AVG(ts.data / ts.avglen), 0) AS 'size'
    FROM
        x.ddp_table_stats AS ts, x.ddp_table_names AS tn
    WHERE
        ts.tableid = tn.id
            AND ts.date = '2017-12-21'
            AND tn.name IN ('nic_stat' , 'agent_app_names')
    GROUP BY name).size -
    (SELECT 
        ROUND(AVG(ts.data / ts.avglen), 0) AS 'size'
    FROM
        x.ddp_table_stats AS ts, x.ddp_table_names AS tn
    WHERE
        ts.tableid = tn.id
            AND ts.date = '2017-12-19'
            AND tn.name IN ('nic_stat' , 'agent_app_names')
    GROUP BY name).size AS result;

Answer 1

你实际上并不需要子查询。相反，我们可以使用条件聚合并对两个连接的表进行单次传递，以获得所需的结果。

SELECT
    name,
    ROUND(AVG(CASE WHEN ts.date = '2017-12-21' THEN ts.data / ts.avglen END) -
    AVG(CASE WHEN ts.date = '2017-12-19' THEN ts.data / ts.avglen END), 0) AS size
FROM
    ddp_table_stats AS ts
INNER JOIN ddp_table_names AS tn
    ON ts.tableid = tn.id
WHERE
    tn.name IN ('nic_stat' , 'agent_app_names')
GROUP BY
    name;

请注意，我也选择了name，因为选择我们分组的列通常是有意义的。另外，我用显式INNER JOIN语法替换了隐式连接语法。

Answer 2

查询中不需要

@drawable/search。

.size

SQL：如何在嵌套查询中获取表的大小

2 个答案: