Question

我有一个查询，添加后会返回其ID

DO
    $do$    
        BEGIN
            IF (SELECT COUNT(*) = 0 FROM COMMENTS WHERE PARENT_ID = ''${this.parent_id}') THEN 
                UPDATE COMMENTS SET HAS_CHILD = TRUE WHERE COMMENT_ID = '${this.parent_id}';
            END IF;
                INSERT INTO COMMENTS(USER_ID, ... , PARENT_ID,  ... , HAS_CHILD) VALUES('${this.user_id}', ... , ${this.parent_id}, ... ', FALSE)
                RETURNING COMMENT_ID;
        END
    $do$

执行请求时，发生错误：ERROR: query has no destination for result data CONTEXT: PL/pgSQL function inline_code_block line 3 at SQL statement SQL state: 42601。没有RETURNING COMMENT_ID;的请求成功。

为什么不使用RETURNING COMMENT_ID;执行请求？

Answer 1

在PL / pgSQL中，必须使用关键字INTO将返回值分配给变量，请参见：
https://www.postgresql.org/docs/9.4/plpgsql-statements.html#PLPGSQL-STATEMENTS-SQL-ONEROW

DO
  $do$
    DECLARE
      result INTEGER := 0;
    BEGIN
      IF (SELECT COUNT(*) = 0 FROM COMMENTS WHERE PARENT_ID = '${this.parent_id}') THEN 
        UPDATE COMMENTS SET HAS_CHILD = TRUE WHERE COMMENT_ID = '${this.parent_id}';
        -- Here you could specify returning value for the UPDATE branch...
      END IF;
      INSERT INTO COMMENTS(USER_ID, ... , PARENT_ID,  ... , HAS_CHILD) VALUES('${this.user_id}', ... , ${this.parent_id}, ... ', FALSE)
        RETURNING COMMENT_ID INTO result;
      RETURN result;
    END
$do$

编辑

或者您可以使用RETURN QUERY语法：

DO
  $do$
    BEGIN
      IF (SELECT COUNT(*) = 0 FROM COMMENTS WHERE PARENT_ID = '${this.parent_id}') THEN 
        UPDATE COMMENTS SET HAS_CHILD = TRUE WHERE COMMENT_ID = '${this.parent_id}';
        -- Here you could specify returning value for the UPDATE branch...
      END IF;
      RETURN QUERY
        INSERT INTO COMMENTS(USER_ID, ... , PARENT_ID,  ... , HAS_CHILD) VALUES('${this.user_id}', ... , ${this.parent_id}, ... ', FALSE)
          RETURNING COMMENT_ID;
    END
$do$

无法插入记录并返回ID

1 个答案:

编辑