How to split the string value in one column and return the result table - sql

Question

Assume we have the following table:
id name member
1 jacky a;b;c
2 jason e
3 kate i;j;k
4 alex null
Now I want to use the sql or t-sql to return the following table:
1 jacky a
1 jacky b
1 jacky c
2 jason e
3 kate i
......
How to do that?
I'm using the MSSQL, MYSQL and Oracle database.

Answer 1

This is the shortest and readable string-to-rows splitter one could devise, and could be faster too.
Use case of choosing pure CTE instead of function, e.g. when you're not allowed to create a function on database :-)
Creating rows generator via function(which could be implemented by using loop or via CTE too) shall still need to use lateral joins(DB2 and Sybase have this functionality, using LATERAL keyword; In SQL Server, this is similar to CROSS APPLY and OUTER APPLY) to ultimately join the splitted rows generated by a function to the main table.
Pure CTE approach could be faster than function approach. The speed metrics lies in profiling though, just check the execution plan of this compared to other solutions if this is indeed faster:
with Pieces(theId, pn, start, stop) AS
(
SELECT id, 1, 1, charindex(';', member)
from tbl
UNION ALL
SELECT id, pn + 1, stop + 1, charindex(';', member, stop + 1)
from tbl
join pieces on pieces.theId = tbl.id
WHERE stop > 0
)
select
t.id, t.name,
word =
substring(t.member, p.start,
case WHEN stop > 0 THEN p.stop - p.start
ELSE 512
END)
from tbl t
join pieces p on p.theId = t.id
order by t.id, p.pn
Output:
ID NAME WORD
1 jacky a
1 jacky b
1 jacky c
2 jason e
3 kate i
3 kate j
3 kate k
4 alex (null)
Base logic sourced here: T-SQL: Opposite to string concatenation - how to split string into multiple records
Live test: http://www.sqlfiddle.com/#!3/2355d/1

Answer 2

Well... let me first introduce you to Adam Machanic who taught me about a Numbers table. He's also written a very fast split function using this Numbers table.
http://dataeducation.com/counting-occurrences-of-a-substring-within-a-string/
After you implement a Split function that returns a table, you can then join against it and get the results you want.

Answer 3

IF OBJECT_ID('dbo.Users') IS NOT NULL
DROP TABLE dbo.Users;
CREATE TABLE dbo.Users
(
id INT IDENTITY NOT NULL PRIMARY KEY,
name VARCHAR(50) NOT NULL,
member VARCHAR(1000)
)
GO
INSERT INTO dbo.Users(name, member) VALUES
('jacky', 'a;b;c'),
('jason', 'e'),
('kate', 'i;j;k'),
('alex', NULL);
GO
DECLARE #spliter CHAR(1) = ';';
WITH Base AS
(
SELECT 1 AS n
UNION ALL
SELECT n + 1
FROM Base
WHERE n < CEILING(SQRT(1000)) --generate numbers from 1 to 1000, you may change it to a larger value depending on the member column's length.
)
, Nums AS --Numbers Common Table Expression, if your database version doesn't support it, just create a physical table.
(
SELECT ROW_NUMBER() OVER(ORDER BY (SELECT 0)) AS n
FROM Base AS B1 CROSS JOIN Base AS B2
)
SELECT id,
SUBSTRING(member, n, CHARINDEX(#spliter, member + #spliter, n) - n) AS element
FROM dbo.Users
JOIN Nums
ON n <= DATALENGTH(member) + 1
AND SUBSTRING(#spliter + member, n, 1) = #spliter
ORDER BY id
OPTION (MAXRECURSION 0); --Nums CTE is generated recursively, we don't want to limit recursion count.