Split (explode) comma delimited column values to rows
Description
Following is Table Structure:
eligibility_table
ID COURSE_ID BRANCH_IDS
1 501 621,622,623
1 502
1 503 625
2 501 621
2 505 650
3 500
Now, I am making new table structure as describe below and inserting course_table,branch_table through eligibility_table. So following, final output I want
course_table
ID COURSE_ID
1 501
1 502
1 503
2 501
2 505
3 500
branch_table
ID BRANCH_ID
1 621
1 622
1 623
1 625
2 621
2 650
Problem:
I am struggling to write SQL QUERY for branch_table. I want to write a query like
INSERT INTO branch_table SELECT --- from eligibility_table --
UPDATED You can do it with SQL like this
INSERT INTO branch_table (id, branch_id)
SELECT e.id, SUBSTRING_INDEX(SUBSTRING_INDEX(e.branch_ids, ',', n.n), ',', -1) branch_id
FROM eligibility_table e CROSS JOIN
(
SELECT a.N + b.N * 10 + 1 n
FROM
(SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) a
,(SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) b
ORDER BY n
) n
WHERE n.n <= 1 + (LENGTH(e.branch_ids) - LENGTH(REPLACE(e.branch_ids, ',', '')))
ORDER BY id, branch_id
- The subquery with an alias of n generates on the fly a sequence of numbers (numbers or tally table) from 1 to 100 in this particular case using
UNION ALL
andCROSS JOIN
. Sometimes it’s handy to have a real tally table in your db. - In outer select innermost
SUBSTRING_INDEX()
gets everything up to n’th element in a list and outerSUBSTRING_INDEX()
extract right most part after a last delimiter effectively getting n-th element itself. -
CROSS JOIN
allows us to produce a set of rows which is a cartesian product (of 100 rows in n and all rows in eligibility_table) - condition in
WHERE
clause filters out all unnecessary rows from the resultset
Note: this query will split up to 100 branch ids. If you need more or less you can adjust a limit by editing the inner subquery
Result in branch_table:
| ID | BRANCH_ID | ------------------ | 1 | 621 | | 1 | 622 | | 1 | 623 | | 1 | 625 | | 2 | 621 | | 2 | 650 |
Here is SQLFiddle demo