mysql - 在 PostgreSQL 中运行 MySQL 查询时出错

Question

我用标准 SQL 编写了查询，并在 MySQL 中测试了它们。

现在，当我尝试在 PostgreSQL 中运行它们时，我遇到了各种各样的错误，我并不真正理解这些错误。 这是在 MySQL 中有效的原始查询:

CREATE VIEW popularCSsections AS (
    SELECT  sect.csid, COUNT(sc.sid) as numStudents
    FROM courseSection sect, studentCourse sc, department d
    WHERE sect.csid = sc.csid 
        AND sect.dcode = d.dcode 
        AND dname = "Computer Science"
    GROUP BY sect.csid
    HAVING numStudents > 2
);

给出这个错误:

psql:a2tables:60: ERROR:  column "Computer Science" does not exist
LINE 8:   AND department.dname = "Computer Science" 
                                 ^

能否请您帮助我了解错误的性质并帮助我修复它们？

---

附加问题:

CREATE VIEW popularCSsections AS (
SELECT  sect.csid, COUNT(sc.sid) as numStudents
FROM courseSection sect, studentCourse sc, department d
WHERE sect.csid = sc.csid 
    AND sect.dcode = d.dcode 
    AND dname = 'Computer Science'
    GROUP BY sect.csid
    HAVING numStudents > 2
);

错误:

psql:a2tables:70: ERROR:  column "numstudents" does not exist
LINE 8:  HAVING numStudents > 2
                ^

Answer 1

您需要用单引号将字符串括起来:

 AND dname = 'Computer Science'

这里发生的事情是双引号被解释为“标识符引号”，表示您希望将内容解释为数据库标识符(列名或表名)。