当我有类似于1, 2, 3...的字符串列表时,我希望将其用作一个列。
Ids
1
2
3
能否通过 SQL 查询实现?
例如:SELECT Ids from (1, 2, 3...)
<- 我知道这个不起作用。
使用任意数字的子查询来拆分您的字符串。您可以使用'1,2,3'代替vals。
SELECT
DISTINCT SUBSTRING_INDEX(SUBSTRING_INDEX(vals, ',', n.digit+1), ',', -1) val
FROM
tt1
INNER JOIN
(SELECT 0 digit UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6) n
ON LENGTH(REPLACE(vals, ',' , '')) <= LENGTH(vals)-n.digit;
SELECT *
FROM
JSON_TABLE(
CONCAT('[', '1,2,3,4', ']'),
"$[*]"
COLUMNS(
ids BIGINT(20) PATH "$"
)
) AS tt
在你的字符串周围加上方括号([]
),以将其转换为JSON数组。然后使用JSON_TABLE
将其转换为表格。有关更多信息,请参见MySQL JSON Table Functions。
您可以使用以下存储过程来拆分由任何字符分隔的字符串:
CREATE PROCEDURE `split_delimited` (
IN inputstr NVARCHAR(1000),
IN delimiter CHAR(1)
)
BEGIN
DROP TEMPORARY TABLE Items;
CREATE TEMPORARY TABLE Items(item NVARCHAR(50));
WHILE LOCATE(delimiter,inputstr) > 1 DO
INSERT INTO Items SELECT SUBSTRING_INDEX(inputstr,delimiter,1);
SET inputstr = REPLACE (inputstr, (SELECT LEFT(inputstr,LOCATE(delimiter,inputstr))),'');
END WHILE;
INSERT INTO Items(item) VALUES(inputstr);
select * from Items;
END
输入:'a,b,c' 输出:a b c
注意,这个答案可能与提问时可用的发布版本的MySQL不兼容。我为那些有兴趣使用递归CTE方法的人添加了此选项以供将来参考。此外,还添加了不规则数据以测试异常处理。
create table test(ids varchar(50));
insert test values('1,2,3');
-- Note: the next_start_pos is the position to the immediate right of the comma.
with recursive cte as
(select locate(',',ids,1)+1 as next_start_pos,
substring(ids,1,locate(',',ids,1)-1) as i
from test
union
select locate(',',t.ids,next_start_pos)+1 ,
case when locate(',',t.ids,next_start_pos) !=0 then substring(t.ids,next_start_pos,locate(',',t.ids,next_start_pos)-next_start_pos)
else substring(t.ids,next_start_pos) end
from test t join cte c
where next_start_pos!=1
)
select next_start_pos, i from cte where i !='';
+----------------+------+
| next_start_pos | i |
+----------------+------+
| 3 | 1 |
| 5 | 2 |
| 1 | 3 |
+----------------+------+
where i !=''
作为一个防错功能。它可以避免由于前导/尾随逗号或连续逗号而导致的空格结果。以下面的案例为例:truncate test;
insert test values(',,,1,,2,3,,,,');
-- run the same query again and we get:
+----------------+------+
| next_start_pos | i |
+----------------+------+
| 6 | 1 |
| 9 | 2 |
| 11 | 3 |
+----------------+------+
-- if the WHERE clause is removed, then we get:
+----------------+------+
| next_start_pos | i |
+----------------+------+
| 2 | |
| 3 | |
| 4 | |
| 6 | 1 |
| 7 | |
| 9 | 2 |
| 11 | 3 |
| 12 | |
| 13 | |
| 14 | |
| 1 | |
+----------------+------+