满足条件时的Sql-Exit CASE语句

Question

以下CASE语句在ID=10的同时更新BET1 ， BET2 ， BET3和BET4 。

$S1=32
$sql="UPDATE TIMER-BOARD1 
set BET1= case when BET1 IS NULL THEN $S1 else BET1 end ,
    BET2= case when BET2 IS NULL THEN $S1 else BET2 end,
    BET3= case when BET3 IS NULL THEN $S1  else BET3 end,
    BET4= case when BET4 IS NULL THEN $S1 else BET4 end
WHERE ID = 10";

当我运行php页面时，我有BET1=32 ， BET2=32 ， BET3=32 ， BET4=32 。

我想要的是让脚本在找到并填充第一个null字段时退出。

即， BET4 = NULL when ID =10 ，从所有BET1 ， BET2 ， BET3 ， BET4 = NULL when ID =10 ，我想在运行php页面时，仅更新BET1=32 。 当我再次运行时，更新BET2=32等。

类似于以下内容：

    $S1=32
    $sql="UPDATE TIMER-BOARD1 
    set BET1= case when BET1 IS NULL THEN $S1 
( EXIT AND DON’T BOTHER ABOUT OTHER CASE      STATEMENTS) else BET1 end ,
       BET2= case when BET2 IS NULL THEN $S1 
(EXIT AND DON’T BOTHER ABOUT OTHER CASE STATEMENTS) else BET2 end,
    BET3= case when BET3 IS NULL THEN $S1 
(EXIT AND DON’T BOTHER ABOUT OTHER CASE STATEMENTS)   else BET3 end,
    BET4= case when BET4 IS NULL THEN $S1 
(EXIT AND DON’T BOTHER ABOUT OTHER CASE STATEMENTS) else BET4 end
    WHERE ID = 10";

结果

Start values: ID=10 ,BET1=NULL, BET2=NULL, BET3=NULL, BET4=NULL.

Run the script 1ST time: ID=10, BET1=32, BET2 =NULL, BET3=NULL, BET4=NULL.

Run the script 2nd time: ID=10, BET1=32, BET2= 32, BET3=NULL, BET4 = NULL.

Run the script 3rd time: ID=10, BET1=32, BET2=32, BET3=32, BET4=NULL.

Run the script 4th time: ID=10, BET1=32, BET2=32, BET3=32, BET4=32.

Run the script 5th time or more: No null field, so no change.

如何编辑脚本以执行上述功能？

编辑

@ InoS Heo

如果你有时间，最后一个问题。

在运行sql之前我有$ S1 = 32。 假设不是32我有苏珊，这当然是一个字符串。

如何更新脚本以适应上述字符串？

$S1 =susan
UPDATE `TIMER-BOARD1`
set 
    ID = @UPDATED := 10,
    BET1 = case when BET1 IS NULL THEN @UPDATED:= susan else BET1 end,
    BET2 = case when @UPDATED = 10 AND BET2 IS NULL THEN @UPDATED:= susan else BET2     end,
…
    BET4 = case when @UPDATED = 10 AND BET4 IS NULL THEN @UPDATED:= susan else BET4 end
WHERE ID = 10;

谢谢。

Answer 1

您正在寻找"UPDATE first NULL column" 。 我认为这可以使用MySQL用户变量来实现。

你能试试吗？

架构和数据

DROP TABLE IF EXISTS `TIMER-BOARD1`;
CREATE TABLE `TIMER-BOARD1` (
  `ID` int(11) NOT NULL,
  `BET1` int(11) DEFAULT NULL,
  `BET2` int(11) DEFAULT NULL,
  `BET3` int(11) DEFAULT NULL,
  `BET4` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

DELETE FROM `TIMER-BOARD1`;
INSERT INTO `TIMER-BOARD1` VALUES (10, NULL, NULL, NULL, NULL),
    (10, 32, NULL, NULL, NULL), (10, 1, 2, NULL, NULL),
    (10, 1, 2, 3, NULL), (10, 1, 2, 3, 4);

初始数据

SELECT * FROM `TIMER-BOARD1`;
+----+------+------+------+------+
| ID | BET1 | BET2 | BET3 | BET4 |
+----+------+------+------+------+
| 10 | NULL | NULL | NULL | NULL |
| 10 |   32 | NULL | NULL | NULL |
| 10 |    1 |    2 | NULL | NULL |
| 10 |    1 |    2 |    3 | NULL |
| 10 |    1 |    2 |    3 |    4 |
+----+------+------+------+------+

UPDATE

UPDATE `TIMER-BOARD1`
set 
    ID = @UPDATED := 10, -- user defined variable which keep track WHETHERE CHANGED OR NOT
    BET1 = case when BET1 IS NULL THEN @UPDATED:= 32 else BET1 end,
    BET2 = case when @UPDATED = 10 AND BET2 IS NULL THEN @UPDATED:=32 else BET2 end,
    BET3 = case when @UPDATED = 10 AND BET3 IS NULL THEN @UPDATED:=32 else BET3 end,
    BET4 = case when @UPDATED = 10 AND BET4 IS NULL THEN @UPDATED:=32 else BET4 end
WHERE ID = 10;

更新的数据

SELECT * FROM `TIMER-BOARD1`;
mysql> SELECT * FROM `TIMER-BOARD1`;
+----+------+------+------+------+
| ID | BET1 | BET2 | BET3 | BET4 |
+----+------+------+------+------+
| 10 |   32 | NULL | NULL | NULL |
| 10 |   32 |   32 | NULL | NULL |
| 10 |    1 |    2 |   32 | NULL |
| 10 |    1 |    2 |    3 |   32 |
| 10 |    1 |    2 |    3 |    4 |
+----+------+------+------+------+

问题

当你想要更新10时仍然有问题。

更新

1.使用一些string_column

我认为你有两个选择

1. 使用字符串列而不是ID列
   • 优点：可以使用一个UPDATE实现
   • 缺点：如果没有更多的字符串列，则无法使用
2. 对每行执行UPDATE
   • 优点：即使没有更多的字符串列也可以使用
   • 缺点：执行几个UPDATE，如果没有PK则不能使用。

我想知道你是否有像string_col这样的字符串列，如下所示。

架构和数据

DROP TABLE IF EXISTS tab;

CREATE TABLE tab (
  `ID` int(11) NOT NULL,
  `BET1` VARCHAR(100) DEFAULT NULL,
  `BET2` VARCHAR(100) DEFAULT NULL,
  `BET3` VARCHAR(100) DEFAULT NULL,
  `BET4` VARCHAR(100) DEFAULT NULL,
  `string_col` VARCHAR(100) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

DELETE FROM tab;
INSERT INTO tab VALUES
    (10, NULL, NULL, NULL, NULL, 'A'),
    (10, 'Alice', NULL, NULL, NULL, 'B'),
    (10, 'Alice', 'Bob', NULL, NULL, 'C'),
    (10, 'Alice', 'Bob', 'Charlie', NULL, 'D'),
    (10, 'Alice', 'Bob', 'Charlie', 'Dave', 'E');

SELECT * FROM tab;
+----+-------+------+---------+------+------------+
| ID | BET1  | BET2 | BET3    | BET4 | string_col |
+----+-------+------+---------+------+------------+
| 10 | NULL  | NULL | NULL    | NULL | A          |
| 10 | Alice | NULL | NULL    | NULL | B          |
| 10 | Alice | Bob  | NULL    | NULL | C          |
| 10 | Alice | Bob  | Charlie | NULL | D          |
| 10 | Alice | Bob  | Charlie | Dave | E          |
+----+-------+------+---------+------+------------+

UPDATE

UPDATE tab
set 
    string_col = @ORIG_STRING_COL := (@UPDATED := string_col),
    BET1 = IF(BET1 IS NULL, @UPDATED := 'Susan', BET1),
    BET2 = IF(@UPDATED != 'Susan' AND BET2 IS NULL, @UPDATED := 'Susan', BET2),
    BET3 = IF(@UPDATED != 'Susan' AND BET3 IS NULL, @UPDATED := 'Susan', BET3),
    BET4 = IF(@UPDATED != 'Susan' AND BET4 IS NULL, @UPDATED := 'Susan', BET4),
    string_col = @ORIG_STRING_COL
WHERE ID = 10;

结果

SELECT * FROM tab;
+----+-------+-------+---------+-------+------------+
| ID | BET1  | BET2  | BET3    | BET4  | string_col |
+----+-------+-------+---------+-------+------------+
| 10 | Susan | NULL  | NULL    | NULL  | A          |
| 10 | Alice | Susan | NULL    | NULL  | B          |
| 10 | Alice | Bob   | Susan   | NULL  | C          |
| 10 | Alice | Bob   | Charlie | Susan | D          |
| 10 | Alice | Bob   | Charlie | Dave  | E          |
+----+-------+-------+---------+-------+------------+

2.为每条记录执行一次UPDATE

使用以下伪代码，您可以实现它。

$res = mysqli_query(SELECT pk_column FROM tab WHERE ID = 10);

while ($row = mysqli_fetch_assoc($res))
{
    $pk_col = $row['pk_column'];

    mysqli_query("SET @UPDATED := ''");

    mysqli_query("UPDATE tab
        SET 
            BET1 = IF(BET1 IS NULL, @UPDATED := 'Susan', BET1),
            BET2 = IF(@UPDATED = '' AND BET2 IS NULL, @UPDATED := 'Susan', BET2),
            BET3 = IF(@UPDATED = '' AND BET3 IS NULL, @UPDATED := 'Susan', BET3),
            BET4 = IF(@UPDATED = '' AND BET4 IS NULL, @UPDATED := 'Susan', BET4)
        WHERE pk_col = $pk_column
    ");

}

前面的代码可以实现客户端或存储过程。

Answer 2

您可以简单地检查其他字段是否已经为null ：

UPDATE TIMER-BOARD1 
SET BET1= case when BET1 IS NULL THEN $S1 else BET1 end ,
    BET2= case when BET1 IS NOT NULL AND BET2 IS NULL THEN $S1 else BET2 end,
    BET3= case when BET1 IS NOT NULL AND BET2 IS NOT NULL AND BET3 IS NULL THEN $S1 else BET3 end,
    BET4= case when BET1 IS NOT NULL AND BET2 IS NOT NULL AND BET3 IS NOT NULL AND BET4 IS NULL THEN $S1 else BET4 end
WHERE ID = 10