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Can Mysql Split a column?

Posted by: admin November 1, 2017 Leave a comment

Questions:

I have a column that has comma separated data:

1,2,3
3,2,1
4,5,6
5,5,5

I’m trying to run a search that would query each value of the CSV string individually.

0<first<5   and  1<second<3  and  2<third<4 

I get that I could return all queries and split it myself and compare it myself.
I’m curious if there is a way to do this so mysql does that processing work.
Thanks!

Answers:

Use

substring_index(`column`,',',1) ==> first value
substring_index(substring_index(`column`,',',-2),',',1)=> second value
substring_index(substring_index(`column`,',',-1),',',1)=> third value

in your where clause.

SELECT * FROM `table`
WHERE 
substring_index(`column`,',',1)<0 
AND
substring_index(`column`,',',1)>5

Questions:
Answers:

It seems to work:

substring_index ( substring_index ( context,’,’,1 ), ‘,’, -1) )

substring_index ( substring_index ( context,’,’,2 ), ‘,’, -1) )

substring_index ( substring_index ( context,’,’,3 ), ‘,’, -1) )

substring_index ( substring_index ( context,’,’,4 ), ‘,’, -1) )

it means 1st value, 2nd, 3rd, etc.

Explanation:
The inner substring_index returns the first n values that are comma separated. So if your original string is “34,7,23,89”, substring_index( context,',', 3) returns “34,7,23”.
The outer substring_index takes the value returned by the inner substring_index and the -1 allows you to take the last value. So you get “23” from the “34,7,23”.
Instead of -1 if you specify -2, you’ll get “7,23”, because it took the last two values.

Example:
select * from MyTable where substring_index(substring_index(prices,',',1),',',-1)=3382;
Here, prices is the name of a column in MyTable.

Questions:
Answers:

Usually substring_index does what you want:

mysql> select substring_index("[email protected]","@",-1);
+-----------------------------------------+
| substring_index("[email protected]","@",-1) |
+-----------------------------------------+
| gmail.com                               |
+-----------------------------------------+
1 row in set (0.00 sec)

Questions:
Answers:

You may get what you want by using the MySQL REGEXP or LIKE.

See the MySQL Docs on Pattern Matching

Questions:
Answers:

As an addendum to this, I’ve strings of the form:
Some words 303

where I’d like to split off the numerical part from the tail of the string.
This seems to point to a possible solution:

http://lists.mysql.com/mysql/222421

The problem however, is that you only get the answer “yes, it matches”, and not the start index of the regexp match.

Questions:
Answers:

Here is another variant I posted on related question. The REGEX check to see if you are out of bounds is useful, so for a table column you would put it in the where clause.

SET @Array = 'one,two,three,four';
SET @ArrayIndex = 2;
SELECT CASE 
    WHEN @Array REGEXP CONCAT('((,).*){',@ArrayIndex,'}') 
    THEN SUBSTRING_INDEX(SUBSTRING_INDEX(@Array,',',@ArrayIndex+1),',',-1) 
    ELSE NULL
END AS Result;
  • SUBSTRING_INDEX(string, delim, n) returns the first n
  • SUBSTRING_INDEX(string, delim, -1) returns the last only
  • REGEXP '((delim).*){n}' checks if there are n delimiters (i.e. you are in bounds)
Questions:
Answers:

It’s working..

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(SUBSTRING_INDEX(SUBSTRING_INDEX(SUBSTRING_INDEX(SUBSTRING_INDEX(SUBSTRING_INDEX(
SUBSTRING_INDEX(SUBSTRING_INDEX(SUBSTRING_INDEX(col,'1', 1), '2', 1), '3', 1), '4', 1), '5', 1), '6', 1)
, '7', 1), '8', 1), '9', 1), '0', 1) as new_col  
FROM table_name group by new_col;