Sql 将列名传递给函数

如何将列名传递给函数，然后在查询中使用该名称

上述代码不起作用：

CREATE OR REPLACE FUNCTION test123(column_name VARCHAR(40)) RETURNS RECORD AS $$
DECLARE   
    rec RECORD ;
BEGIN
    SELECT * INTO rec FROM my_table WHERE column_name=1 LIMIT 1;
    RETURN rec;
END;
$$ LANGUAGE plpgsql;

---

如果要在函数内部的查询中使用函数参数作为标识符，则需要动态执行查询：

error: operator does not exist: character varying = integer

或者更短一些：

CREATE OR REPLACE FUNCTION test123(column_name VARCHAR(40)) RETURNS RECORD AS $$
DECLARE   
    rec RECORD;
BEGIN
    EXECUTE format('SELECT * FROM my_table WHERE %I = 1 LIMIT 1', column_name)
    INTO rec;
    RETURN rec;
END;
$$ LANGUAGE plpgsql;

---

为此，您需要动态SQL。有关一些示例，请参见手册：

CREATE OR REPLACE FUNCTION test123(column_name VARCHAR(40)) RETURNS RECORD AS $$
BEGIN
    RETURN QUERY EXECUTE format('SELECT * FROM my_table WHERE %I = 1 LIMIT 1', column_name);
END;
$$ LANGUAGE plpgsql;