为什么我收到错误“SQL 命令未正确结束”？

Question

这是我尝试在 oracle live SQL 中运行的 SQL 查询：

SELECT yearly,branch,SUM(package_offered) AS "PACKAGE_OFFERED"
FROM PLACEMENT_FACTS AS PAF ,STUDENT AS ST, TIME_PERIOD AS TP
WHERE PAF.STUDENT_ID = ST.STUDENT_ID AND PAF.TIME_PERIOD_ID = TP.TIME_PERIOD_ID AND BRANCH = 'MECH'
GROUP BY yearly;

Answer 1

编写这个查询的正确方法是这样的：

SELECT yearly, branch, SUM(package_offered) AS PACKAGE_OFFERED
FROM PLACEMENT_FACTS PAF JOIN
     STUDENT ST
     ON PAF.STUDENT_ID = ST.STUDENT_ID JOIN
     TIME_PERIOD TP
     ON PAF.TIME_PERIOD_ID = TP.TIME_PERIOD_ID
WHERE BRANCH = 'MECH'
GROUP BY yearly, branch;

您应该限定yearly 和branch，以便清楚它们来自哪些表。

注意事项：

• 从不在FROM 子句中使用逗号。 始终使用适当的显式、标准、可读的JOIN 语法。
• 您不需要转义列别名。
• 您应该限定所有列名。
• SELECT 中的所有未聚合列都应在 GROUP BY 中。