Question

我需要一些帮助制作这个MySQL Cursor，我一直在关注本指南：http://www.mysqltutorial.org/mysql-cursor/。我试图让游标迭代一个表，并一次创建一行名称列表。

CREATE PROCEDURE build_people_table ( @people varchar(4000))
AS
BEGIN
DECLARE @v_finished INT;
    DECLARE @v_name nvarchar(255);


    --Main Cursor
    DECLARE people_cursor CURSOR FOR
    SELECT [Person Name]
    FROM [dbo].[People];

     -- declare NOT FOUND handler
 DECLARE CONTINUE HANDLER 
        FOR NOT FOUND SET @v_finished = 1;


    OPEN people_cursor;

    get_name: LOOP

    FETCH people_cursor INTO @v_name ;

    IF @v_finished = 1 THEN
    LEAVE get_name;
    END IF;

    SET @people = CONCAT(@v_name,';',@people);
    END LOOP get_name;

    CLOSE people_cursor;

END

mySQL错误消息

Msg 156, Level 15, State 1, Procedure build_people_table, Line 41
Incorrect syntax near the keyword 'CONTINUE'.
Msg 136, Level 15, State 1, Procedure build_people_table, Line 41
Cannot use a CONTINUE statement outside the scope of a WHILE statement.
Msg 102, Level 15, State 1, Procedure build_people_table, Line 47
Incorrect syntax near 'LOOP'.
Msg 156, Level 15, State 1, Procedure build_people_table, Line 56
Incorrect syntax near the keyword 'THEN'.
Msg 102, Level 15, State 1, Procedure build_people_table, Line 61
Incorrect syntax near 'LOOP'.
Msg 156, Level 15, State 1, Procedure build_people_table, Line 74
Incorrect syntax near the keyword 'END'.

Answer 1

这显示了它在Mysql中的端到端（你所说的技术）。

注意，最好使用

select group_concat(`Person Name`) from People;

为此。但无论出于何种原因，您似乎都想为它编写存储过程，可能是为了学习目的。重要的是要注意游标就像非常慢。

另请注意，输出缓冲区（ out 参数）很有可能溢出。有很多数据可以进入那里。所以我把它从varchar（4000）更改为TEXT。

模式

create table People
(   id int auto_increment primary key,
    `Person Name` varchar(200)
); 

insert People(`Person Name`) values ('John Henry'),('Kim Billings'),('Gertrude Smith');

存储过程

drop procedure if exists build_people_table;
DELIMITER $$
CREATE PROCEDURE build_people_table ( OUT people_out TEXT)
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE v_name nvarchar(255);
    -- DECLARE bFirst boolean DEFAULT TRUE;


    -- Main Cursor
    DECLARE people_cursor CURSOR FOR
    SELECT `Person Name`
    FROM `People`;

    -- declare NOT FOUND handler
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=TRUE;


    OPEN people_cursor;
    set @people='';

    get_name: LOOP

        FETCH people_cursor INTO v_name;

        IF done THEN
            LEAVE get_name;
        END IF;
        SET @people:= CONCAT(v_name,";",@people);
        -- SET @people:= CONCAT(@people,";",v_name);
    END LOOP get_name;

    CLOSE people_cursor;
    set people_out:=@people;
    -- select @people; -- used for debugging
END
$$
DELIMITER ;

测试

set @saveHere:='';
call build_people_table(@saveHere);
select @saveHere; -- show results

'Gertrude Smith;Kim Billings;John Henry;'

ERROR消息156，级别15，状态1，关键字'CONTINUE'附近的语法不正确

1 个答案:

模式

存储过程

测试