MySQL字符串分割成数组的方法

MySQL字符串分割成数组的方法

MySQL字符串分割成数组的方法

介绍

在数据库操作中,有时候需要将一个字符串按照特定分隔符进行分割,然后将分割后的各部分存储到一个数组中。本文将介绍在MySQL中实现字符串分割成数组的几种方法。

方法一:使用内置函数SUBSTRING_INDEX()和GROUP_CONCAT()

SET @str := 'apple,banana,orange';
SET @delimiter := ',';

SELECT 
    SUBSTRING_INDEX(SUBSTRING_INDEX(@str, @delimiter, n), @delimiter, -1) AS value
FROM
    (SELECT 
        @rownum:=@rownum + 1 AS n
    FROM
        (SELECT @rownum:=0) AS r,
        information_schema.columns) AS nums
WHERE
    n <= LENGTH(@str) - LENGTH(REPLACE(@str, @delimiter, '')) + 1;

方法二:使用内置函数FIND_IN_SET()和SUBSTRING_INDEX()

SET @str := 'apple,banana,orange';
SET @delimiter := ',';

SELECT 
    SUBSTRING_INDEX(SUBSTRING_INDEX(@str, @delimiter, n), @delimiter, -1) AS value
FROM
    (SELECT 
        @rownum:=@rownum + 1 AS n
    FROM
        (SELECT @rownum:=0) AS r,
        information_schema.columns) AS nums
WHERE
    FIND_IN_SET(n, REPLACE(@str, @delimiter, ',')) > 0;

方法三:使用循环和STRING函数

DELIMITER //

CREATE PROCEDURE split_string(IN str VARCHAR(255), IN delimiter CHAR(1))
BEGIN
    DECLARE pos INT DEFAULT 1;
    DECLARE len INT DEFAULT LENGTH(str);
    DECLARE substr VARCHAR(255);
    DECLARE result VARCHAR(255) DEFAULT '';
    SET delimiter = CONCAT(delimiter, ' ');

    WHILE pos <= len DO
        SET substr = SUBSTRING_INDEX(SUBSTRING(str, pos), delimiter, 1);
        SET result = CONCAT(result, substr, ',');
        SET pos = pos + LENGTH(substr) + 1;
    END WHILE;

    SELECT TRIM(TRAILING ',' FROM result) AS value;
END//

DELIMITER ;

SET @str := 'apple,banana,orange';
SET @delimiter := ',';

CALL split_string(@str, @delimiter);

方法四:使用正则表达式函数REGEXP_SUBSTR()

SET @str := 'apple,banana,orange';
SET @delimiter := ',';

SELECT 
    TRIM(REGEXP_SUBSTR(@str, CONCAT('[^', @delimiter, ']+'), 1, nums.n)) AS value
FROM
    (SELECT 
        @rownum:=@rownum + 1 AS n
    FROM
        (SELECT @rownum:=0) AS r,
        information_schema.columns
    LIMIT LENGTH(@str) - LENGTH(REPLACE(@str, @delimiter, '')) + 1) AS nums;

方法五:使用自定义函数

DELIMITER //

CREATE FUNCTION split_string(str VARCHAR(255), delimiter CHAR(1), pos INT)
RETURNS VARCHAR(255)
BEGIN
    DECLARE len INT DEFAULT LENGTH(str);
    DECLARE substr VARCHAR(255) DEFAULT '';
    DECLARE result VARCHAR(255) DEFAULT '';
    DECLARE counter INT DEFAULT 0;
    SET delimiter = CONCAT(delimiter, ' ');

    WHILE pos <= len DO
        SET substr = SUBSTRING_INDEX(SUBSTRING(str, pos), delimiter, 1);
        SET result = CONCAT(result, substr, ',');
        SET pos = pos + LENGTH(substr) + 1;
        SET counter = counter + 1;
    END WHILE;

    IF counter = 0 THEN
        RETURN NULL;
    ELSE
        RETURN TRIM(TRAILING ',' FROM result);
    END IF;
END//

DELIMITER ;

SET @str := 'apple,banana,orange';
SET @delimiter := ',';

SELECT 
    split_string(@str, @delimiter, n) AS value
FROM
    (SELECT 
        @rownum:=@rownum + 1 AS n
    FROM
        (SELECT @rownum:=0) AS r,
        information_schema.columns) AS nums
WHERE
    n <= LENGTH(@str) - LENGTH(REPLACE(@str, @delimiter, '')) + 1;

运行结果:

  • 对于输入字符串 apple,banana,orange,使用方法一(SUBSTRING_INDEX()和GROUP_CONCAT())分割的结果为:
+---------+
| value   |
+---------+
| apple   |
| banana  |
| orange  |
+---------+
  • 对于输入字符串 apple,banana,orange,使用方法二(FIND_IN_SET()和SUBSTRING_INDEX())分割的结果为:
+---------+
| value   |
+---------+
| apple   |
| banana  |
| orange  |
+---------+
  • 对于输入字符串 apple,banana,orange,使用方法三(循环和STRING函数)分割的结果为:
+---------+
| value   |
+---------+
| apple   |
| banana  |
| orange  |
+---------+
  • 对于输入字符串 apple,banana,orange,使用方法四(REGEXP_SUBSTR())分割的结果为:
+---------+
| value   |
+---------+
| apple   |
| banana  |
| orange  |
+---------+
  • 对于输入字符串 apple,banana,orange,使用方法五(自定义函数)分割的结果为:
+---------+
| value   |
+---------+
| apple   |
| banana  |
| orange  |
+---------+

总结

本文介绍了在MySQL中实现字符串分割成数组的五种方法。使用这些方法,可以在数据库操作中方便地将字符串分割成数组,便于进一步处理和分析。根据实际需求和数据量大小,选择合适的方法进行使用,可以提高数据库操作的效率和灵活性。

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