SELECT agent.name AS agent, operation.name AS operation
FROM agent, operation
WHERE agent.operationID = operation.operationID
ORDER BY agent.name;别名应该是这样吧"agent.name AS agent" agent为agent.name 的别名
FROM agent, operation
WHERE agent.operationID = operation.operationID
ORDER BY agent.name;别名应该是这样吧"agent.name AS agent" agent为agent.name 的别名
一个 SELECT 表达式可以使用 AS 指定一个别名。别名可以当作表达式的列名,用于 ORDER BY 或 HAVING 子句中
一个 WHERE 子句中使用一个列别名是不允许的,因为,当 WHERE 子句被执行时,列值可能还没有被计算确定