How to Efficiently Split and Filter a Comma-Separated VARCHAR Column in SQL?

Splitting a VARCHAR Column into Multiple Values in SQL

The VARCHAR data type in SQL allows for the storage of variable-length character data. Often, it is necessary to split a VARCHAR column into multiple values to facilitate data filtering or other operations.

Consider the following example:

SELECT 
  AD_Ref_List.Value
FROM AD_Ref_List
WHERE AD_Ref_List.AD_Reference_ID= 1000448

This query retrieves a column named "Value" from the table "AD_Ref_List" where the column "AD_Reference_ID" is equal to 1000448. The result is a list of values:

CO,VO

However, the requirement is to limit the results based on values stored in a different table, "xx_insert":

SELECT xx_insert.XX_DocAction_Next
  FROM xx_insert
  WHERE xx_insert_id = 1000283

The result of this query is:

CO

The challenge lies in modifying the original query to incorporate the values from "xx_insert" while maintaining the comma-separated format. The initial attempt transformed the values into a delimited string:

AD_Ref_List.Value IN ('CO,VO')

Which is not the desired result.

Solution:

To address this issue, the values in the IN clause should be wrapped with the appropriate delimiter and checked against a comma-separated list also enclosed with delimiters:

SELECT r.Value
FROM   AD_Ref_List r
       INNER JOIN xx_insert x
       ON ( ',' || x.XX_DocAction_Next || ',' LIKE '%,' || r.value || ',%' )
WHERE  r.AD_Reference_ID = 1000448
AND    x.xx_insert_id    = 1000283;

This technique allows for the identification of values that match the comma-separated list. Alternatively, a more efficient approach using row-value filtering can also be employed:

SELECT Value
FROM   AD_Ref_List
WHERE  AD_Reference_ID = 1000448
AND    value IN (
  SELECT REGEXP_SUBSTR( XX_DocAction_Next, '[^,]+', 1, LEVEL )
  FROM   xx_insert
  WHERE  xx_insert_id    = 1000283
  CONNECT BY LEVEL <= REGEXP_COUNT( XX_DocAction_Next, '[^,]+' )
);

Both solutions effectively split the VARCHAR column into multiple values and filter based on the specified values, resolving the issue encountered in the initial query.

The above is the detailed content of How to Efficiently Split and Filter a Comma-Separated VARCHAR Column in SQL?. For more information, please follow other related articles on the PHP Chinese website!