OceanBase 存在條件

存在條件（EXISTS Conditions）用于測(cè)試子查詢中是否存在指定的行。

語(yǔ)法

EXISTS (subquery)

如果子查詢至少返回一行，則說明存在您想要的數(shù)據(jù)。

示例

SELECT department_id FROM departments d WHERE EXISTS (SELECT * FROM employees e 
WHERE d.department_id = e.department_id) ORDER BY department_id;