MariaDB为ROW类型的变量动态提取列

据我在mariadb文档中看到的，您不能直接执行。行类型也没有循环支持。但是，我建议只保留信息_SCHEMA.COLUMNS游标并生成动态选择，如

读循环：循环 将c_列提取到col中； 如果这样做的话 离开read_循环； 如果结束； 将@SQL:=CONCAT'SELECT'，col'设置为@colval FROM`'，在'tbl'名称中，'WHERE row\u id='，在'u row\u id'中； 从@SQL准备stmt； 使用col执行stmt； 解除分配准备stmt； 设置@create_list:=CONCAT@create_list","col","col","col","colval",； 结束循环读取循环； 由于您只拆分一个表行，这就足够了

更新：有额外的信息，它可以这样做。重新思考之后：

set@SQL:=“选择CONCAT”； 读循环：循环 将c_列提取到col中； 如果这样做的话 离开read_循环； 如果结束； SET@SQL:=CONCAT@SQL，“\\”，列，“\\”，“\\”，列，“\\”，”； 结束循环读取循环； set@SQL:=substring@SQL，1，CHAR_LENGTH@SQL - 3; set@SQL:=concat@SQL，进入@create_list FROM`'，在` tbl_name'，` WHERE row_id='，在` row_id'中； 从@SQL准备stmt； 使用col执行stmt； 解除分配准备stmt；

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@谢谢你的支持。我对你的答案做了一些调整，增加了对空字符和转义字符的支持。以下是最后的程序

delimiter $$

CREATE OR REPLACE PROCEDURE  `populate_audit_helper_new3`(
    IN in_db_name VARCHAR(100),
    IN in_tbl_name VARCHAR(100),
    IN in_row_id INT(10)
)
proc: BEGIN
        DECLARE done INT DEFAULT FALSE;
        DECLARE col CHAR(40);
        DECLARE val TEXT(10000);
        DECLARE q TEXT(100000);     

        DECLARE c_columns CURSOR FOR 
            SELECT column_name
            FROM INFORMATION_SCHEMA.COLUMNS
            WHERE TABLE_SCHEMA = in_db_name
                AND table_name = in_tbl_name
            ORDER BY ordinal_position;

        DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

        OPEN c_columns;

        SET q = "";
        SET @val = "";

        read_loop: LOOP
            FETCH c_columns INTO col;

            IF done THEN
                LEAVE read_loop;
            END IF;
            SET q = CONCAT(q, "'", col, "','|', IFNULL(QUOTE(", col, "), ''),'$'");

        END LOOP read_loop;

        SET q = TRIM(TRAILING "," FROM q);

        SET q = CONCAT("CONCAT(", q, ") INTO @val");

        EXECUTE IMMEDIATE CONCAT("SELECT ", q , " FROM ", in_tbl_name, " WHERE row_id = ", in_row_id);

        IF @val = '' THEN
            LEAVE proc;
        END IF;

        SELECT CONCAT("'", REPLACE(@val, "|", "',"), "'") INTO @val;

        SELECT REPLACE(@val, "$", ",") INTO @val;

        SELECT TRIM(TRAILING ",'" FROM @val) INTO @val;

        EXECUTE IMMEDIATE CONCAT("INSERT INTO x1 SET dynamic_cols_l1 = COLUMN_CREATE(", @val, ")" );

        CLOSE c_columns;
 END$$

---

我不明白，你在读循环中做了什么你得到了专栏名和什么？可以在开始时执行stmt。rec是ROW类型的变量，因此它有多个列。所以我想在循环的每次迭代中一个接一个地获取每个列，列的名称也是一个变量'col'，它在每次迭代中都会改变，但rec不会。我试过准备好的语句，它不起作用。错误是rec是游标类型，而不是表。您必须做的是首先在所有列中运行，然后在所有行中运行。这更合理，但我仍然没有得到你想要达到的目标。我从未见过带有SELECt*的光标。你应该用具体的数据示例来解释你试图实现的目标。我删除了mysql标记，因为mysql没有行数据类型或语法类型。该过程在MySQL上不起作用。@nbk我已更新了计划生成的最终查询。这里唯一的问题是，它在每次迭代中插入rec.name的值。相反，我想要rec.col的值，其中col是一个变量。col的值之一是name。不能使用？列名的占位符。在准备语句时，所有标识符表、列等都必须固定。但是，您应该在\u row\u id中参数化，而不是将其连接到SQL字符串中。但你不是。不，我不应该。它是存储过程的参数，所以保持它的静态是更好的主意。感谢您关于列名的注释howeverThis将为每一列运行一个查询，我不想这样做，因为我计划在所有表的每次更新上通过触发器调用此过程。这就是您最初在问题中所做的

delimiter $$

CREATE OR REPLACE PROCEDURE  `populate_audit_helper_new3`(
    IN in_db_name VARCHAR(100),
    IN in_tbl_name VARCHAR(100),
    IN in_row_id INT(10)
)
proc: BEGIN
        DECLARE done INT DEFAULT FALSE;
        DECLARE col CHAR(40);
        DECLARE val TEXT(10000);
        DECLARE q TEXT(100000);     

        DECLARE c_columns CURSOR FOR 
            SELECT column_name
            FROM INFORMATION_SCHEMA.COLUMNS
            WHERE TABLE_SCHEMA = in_db_name
                AND table_name = in_tbl_name
            ORDER BY ordinal_position;

        DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

        OPEN c_columns;

        SET q = "";
        SET @val = "";

        read_loop: LOOP
            FETCH c_columns INTO col;

            IF done THEN
                LEAVE read_loop;
            END IF;
            SET q = CONCAT(q, "'", col, "','|', IFNULL(QUOTE(", col, "), ''),'$'");

        END LOOP read_loop;

        SET q = TRIM(TRAILING "," FROM q);

        SET q = CONCAT("CONCAT(", q, ") INTO @val");

        EXECUTE IMMEDIATE CONCAT("SELECT ", q , " FROM ", in_tbl_name, " WHERE row_id = ", in_row_id);

        IF @val = '' THEN
            LEAVE proc;
        END IF;

        SELECT CONCAT("'", REPLACE(@val, "|", "',"), "'") INTO @val;

        SELECT REPLACE(@val, "$", ",") INTO @val;

        SELECT TRIM(TRAILING ",'" FROM @val) INTO @val;

        EXECUTE IMMEDIATE CONCAT("INSERT INTO x1 SET dynamic_cols_l1 = COLUMN_CREATE(", @val, ")" );

        CLOSE c_columns;
 END$$

delimiter $$

CREATE OR REPLACE PROCEDURE  `populate_audit_helper_new5`(
    IN in_db_name VARCHAR(100),
    IN in_tbl_name VARCHAR(100),
    IN in_row_id INT(10)
)
proc: BEGIN

    DECLARE done INT DEFAULT FALSE;
    DECLARE create_list TEXT(10000);
    DECLARE col TEXT(10000);

    DECLARE c_columns CURSOR FOR 
        SELECT column_name
        FROM INFORMATION_SCHEMA.COLUMNS
        WHERE TABLE_SCHEMA = in_db_name
            AND table_name = in_tbl_name
        ORDER BY ordinal_position;

    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN c_columns;

    set @SQL := 'SELECT CONCAT(\'';

    read_loop: LOOP
        FETCH c_columns INTO col;
        IF done THEN
           LEAVE read_loop;
        END IF;
        SET @SQL := CONCAT(@SQL, "\\'", col, "\\'\', \', \', IFNULL(QUOTE(", col, "), \'\'), '\, ");
    END LOOP read_loop;

    set @SQL := substring(@SQL, 1, CHAR_LENGTH(@SQL) - 5);

    set @SQL := concat(@SQL, ') into @create_list FROM `', in_tbl_name, '` WHERE row_id = ', in_row_id);

    PREPARE stmt FROM @SQL;
    execute stmt;
    DEALLOCATE PREPARE stmt;

    EXECUTE IMMEDIATE CONCAT("INSERT INTO x1 SET dynamic_cols_l1 = COLUMN_CREATE(", @create_list, ")" );

    CLOSE c_columns;

END$$