Can we use LIKE in subquery instead of IN - sql

Question

I am using following sql query
SELECT * FROM TestTable WHERE keyword IN ( Select Tags from Tags)
keyword in table are stored as keyword1, keyword2, keyword3
If it was single keyword the above query works fine but i have multiple keywords and i need to search each one of them in the
I dont thing above query is giving me right result as i am comparing
keyword1, keyword2, keyword3 with IN (keyword1, keyword2, keyword3) which wont match i tried o use instead
SELECT * FROM TestTable WHERE keyword LIKE ( Select Tags from Tags)
But it generates error
Subquery returned more than 1 value. This is not permitted when the
subquery follows =, !=, <, <= , >, >= or when the subquery is used as
an expression. The statement has been terminated.
can can i make it work so it loops through each keyword in table1, Table2 is tempTable and has these keyword1, keyword2, keyword3 in three rows
SQL FIDDLE
Fiddle is with sample data

Answer 1

You can do like following if you want to use pattern match.
Using EXISTS
SELECT * FROM TABLE1 T1
WHERE EXISTS
(
SELECT 1 FROM TABLE2 T2 WHERE T1.Keyword LIKE '%' + T2.keyword + '%'
)
Using JOIN
SELECT * FROM TABLE1 T1
INNER JOIN TABLE2 T2 ON T1.Keyword LIKE '%' + T2.keyword + '%'
If it is exact match, you ca do like following.
SELECT * FROM TABLE1 T1
INNER JOIN TABLE2 T2 ON T1.Keyword = T2.keyword

Answer 2

About your error:
Your subquery gives you multiple results and the LIKE operator cant compare more then 1 to 1. The IN operator was a good idea, but
If you are looking for something in table2 that matches EXACTLY a record (or more) in table1 this is your target:
SELECT *
FROM TABLE1
INNER JOIN TABLE2 ON TABLE2.keyword = TABLE1.keyword
If you are looking for anything in table2 that is SIMILAR to one or more records to the table1 use this:
SELECT *
FROM TABLE1
INNER JOIN TABLE2 ON TABLE2.keyword+'%' LIKE TABLE1.keyword

Answer 3

if you are on sql server or +, use string_split function, else :
create function split:
CREATE FUNCTION [dbo].[fn_split](
#str VARCHAR(MAX),
#delimiter CHAR(1)
)
RETURNS #returnTable TABLE (idx INT PRIMARY KEY IDENTITY, item VARCHAR(8000))
AS
BEGIN
DECLARE #pos INT
SELECT #str = #str + #delimiter
WHILE LEN(#str) > 0
BEGIN
SELECT #pos = CHARINDEX(#delimiter,#str)
IF #pos = 1
INSERT #returnTable (item)
VALUES (NULL)
ELSE
INSERT #returnTable (item)
VALUES (rtrim(ltrim(SUBSTRING(#str, 1, #pos-1))))
SELECT #str = SUBSTRING(#str, #pos+1, LEN(#str)-#pos)
END
RETURN
END
Split your values like it:
select * from tmp20180308 t1 CROSS APPLY fn_split(t1.keyword, ',') t2
inner join table2 t3 on t3.keyword=t2.item
and do your joins with other table

Answer 4

It can be done using Dynamic SQL. Check different methods for the one that has performance advantage:
SQLFiddle:
Declare #keywords as nvarchar(max)
Declare #Sql as nvarchar(max)
select #keywords =
stuff((
select distinct ' or [Tags] like ''%' + [tags] + '%'''
from [tags]
for xml path('')
),1,3,'')
set #Sql = 'SELECT * FROM [TestTable] WHERE ' + #keywords
exec(#Sql)
Not Fiddle:
create table a (keyword varchar(20))
create table b (keyword varchar(20))
insert into a values ('the'), ( 'quick'), ( 'brown'), ( 'fox'), ( 'jumped'), ( 'over'), ( 'the'), ( 'lazy'), ( 'dog')
insert into b values ('the'), ( 'quic'), ( 'browns'), ( 'x'), ( 'jumped'), ('quick,brown,fox')
Declare #keywords as nvarchar(max)
Declare #Sql as nvarchar(max)
select #keywords =
stuff((
select distinct ' or keyword like ''%' + [keyword] + '%'''
--select distinct ' or keyword = ''' + [keyword] + '''' --if exact match is required
from b
for xml path('')
),1,3,'')
set #Sql = 'SELECT * FROM a WHERE ' + #keywords
exec(#Sql)