Split column value into substrings and search for pattern in SQL - sql

Question

I have a table like this:
campaign
code
AL2330GH_HDKASL_QCLKP
NULL
JPDJK34_QPKSLL_QKPAL
NULL
QCK32_SDSKDS_TLLKA
NULL
I want to update the above table by populating the column 'code' with a substring in column 'campaign' which starts with 'AL', 'QC', or 'QP'. All the column values have 3 substrings separated by an '_'. If none of the substrings matches with the provided values, then keep the 'code' column value as NULL. And if multiple matches happen, take the first substring.
Desired Output:
campaign
code
AL2330GH_HDKASL_QCLKP
AL2330GH
JPDJK34_QPKSLL_QKPAL
QPKSLL
QCK32_SDSKDS_TLLKA
QCK32
Link to try out the problem: https://www.db-fiddle.com/f/8qoFDL1RmjwpwFNP3LP4eK/1

Answer 1

Here's a method using OPENJSON():
;WITH src AS
(
SELECT campaign, value, code,
rn = ROW_NUMBER() OVER (PARTITION BY campaign ORDER BY [key])
FROM
(
SELECT campaign, [key], value, code
FROM dbo.SomeTable
CROSS APPLY OPENJSON(CONCAT('["',
REPLACE(STRING_ESCAPE(campaign,'JSON'),'_','","'),'"]')) AS j
) AS x WHERE LEFT(value,2) IN ('AL','QC','QP')
)
UPDATE src SET code = value WHERE rn = 1;
Example db<>fiddle

Answer 2

You can try to use STRING_SPLIT with CROSS APPLY and ROW_NUMBER window function to make it.
CHARINDEX function will find the first match position value then we can put the split value in the first parameter, then we can find which string the first appearance.
SELECT campaign,value
FROM (
SELECT *,
ROW_NUMBER() OVER(PARTITION BY campaign ORDER BY CHARINDEX(v.value,t1.campaign)) rn
FROM mainTable t1
CROSS APPLY STRING_SPLIT(t1.campaign,'_') v
WHERE (value LIKE 'AL%'
OR value LIKE 'QC%'
OR value LIKE 'QP%')
) t1
WHERE rn = 1
If you want to UPDATE values you can try UPDATE like this.
UPDATE t1
SET
code = value
FROM (
SELECT *,
ROW_NUMBER() OVER(PARTITION BY campaign ORDER BY CHARINDEX(v.value,t1.campaign)) rn
FROM mainTable t1
CROSS APPLY STRING_SPLIT(t1.campaign,'_') v
WHERE (value LIKE 'AL%'
OR value LIKE 'QC%'
OR value LIKE 'QP%')
) t1
WHERE rn = 1
sqlfiddle

Answer 3

Please try the following solution.
It is using XML and XQuery for tokenization. XML/XQuery data model is based on ordered sequences. Exactly what we need for the scenario.
SQL
-- DDL and sample data population, start
DECLARE #tbl TABLE (id INT IDENTITY PRIMARY KEY, campaign varchar(50), code varchar(20));
INSERT INTO #tbl (campaign, code) VALUES
('AL2330GH_HDKASL_QCLKP', NULL),
('JPDJK34_QPKSLL_QKPAL', NULL),
('QCK32_SDSKDS_TLLKA', NULL);
-- DDL and sample data population, end
DECLARE #separator CHAR(1) = '_';
UPDATE t
SET code = c.query('
for $x in /root/r[substring(text()[1],1,2)=("AL","QC","QP")]
return $x').value('(/r/text())[1]', 'VARCHAR(20)')
FROM #tbl AS t
CROSS APPLY (SELECT TRY_CAST('<root><r><![CDATA[' +
REPLACE(campaign, #separator, ']]></r><r><![CDATA[') +
']]></r></root>' AS XML)) AS t1(c);
Output
+----+-----------------------+----------+
| id | campaign | Code |
+----+-----------------------+----------+
| 1 | AL2330GH_HDKASL_QCLKP | AL2330GH |
| 2 | JPDJK34_QPKSLL_QKPAL | QPKSLL |
| 3 | QCK32_SDSKDS_TLLKA | QCK32 |
+----+-----------------------+----------+