使用子查询
SQL允许将查询语句嵌套在其他查询语句当中,即子查询,子查询是从内层向外层查询。
例:
SELECT ts_code,COUNT(*)
FROM StockBasicData
WHERE ts_code IN (
SELECT ts_code
FROM `BasicLevel`
WHERE `level` = 9)
GROUP BY ts_code
使用子查询
SQL允许将查询语句嵌套在其他查询语句当中,即子查询,子查询是从内层向外层查询。
例:
SELECT ts_code,COUNT(*)
FROM StockBasicData
WHERE ts_code IN (
SELECT ts_code
FROM `BasicLevel`
WHERE `level` = 9)
GROUP BY ts_code