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。