sql - Column doens't exists in PostgreSQL (WHERE column_name = column_value)

Question

I have the following table in PostgreSQL:

id and grade are INTs, note and subject both VARCHARs

When I run the command:

SELECT * FROM grades 
WHERE subject = "latin";

I get the following error:

In pgAdmin4: ERROR: column "latin" does not exist LINE 2: WHERE subject = "latin" ^ SQL state: 42703 Character: 37

And in cmd: ERROR: column "latin" does not exist LINE 1: SELECT * FROM upisi WHERE subject = "latin";

I'm coming from MySQL so I thought this would work. Works fine if I put grade = something in the WHERE clause. Any idea why this might be the case?

标签： sqlpostgresqlstring-constant

Answer 1

字符常量需要单引号。（双引号用于引用标识符）

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SELECT * FROM grades 
WHERE subject = 'latin';

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如果您使用WHERE subject = "latin"，则 DBMS 期望“latin”是一个列名，但事实并非如此。