将动态查询保存到 postgres 存储过程中的变量

Question

我有以下 postgres 存储过程：

CREATE OR REPLACE PROCEDURE
schema.MyProcedure()
AS $$

DECLARE 
    RowCount int;
    
BEGIN
    
    SELECT cnt INTO RowCount 
    FROM (
        SELECT COUNT(*) AS cnt
        FROM MySchema.MyTable
        ) AS sub;
    
    RAISE NOTICE 'RowCount: %', RowCount;
    
END;
$$
LANGUAGE plpgsql;

它“打印”出静态 table MySchema.MyTable 的行数。它是怎么做到的，所以我将 Table 和架构名称作为输入传递。

例如：

CREATE OR REPLACE PROCEDURE
schema.MyProcedure(MySchema_In varchar, MyTable_In varchar)
AS $$

DECLARE 
    RowCount int;
    
BEGIN
    
    SELECT cnt INTO RowCount 
    FROM (
        SELECT COUNT(*) AS cnt
        FROM || **MySchema_In** || . || **MyTable_In** || 
        ) AS sub;
    
    RAISE NOTICE 'RowCount: %', RowCount;
    
END;
$$
LANGUAGE plpgsql;

Answer 1

您应该使用 format() 而不是将字符串与 || 连接然后 EXECUTE ... INTO 以获得查询结果，例如

CREATE OR REPLACE PROCEDURE MyProcedure(MySchema_In varchar, MyTable_In varchar)
AS $$
DECLARE RowCount int;
BEGIN
  EXECUTE FORMAT('SELECT count(*) FROM %I.%I',,) INTO RowCount;
  RAISE NOTICE 'RowCount: %', RowCount;    
END;
$$
LANGUAGE plpgsql;

将动态查询保存到 postgres 存储过程中的变量

Save dynamic query to variable in postgres stored procedure

postgresql

stored-procedures

plpgsql

dynamicquery