If the answer is helpful, please click " Accept Answer" and upvote it. Then use GROUP BY to consolidate categories and COUNT to determine if match (es) exist: SELECT categories.id, categories.title, CASE WHEN COUNT (prodvscats.id) 0 THEN 0 ELSE 1 END AS productexists. If you have any question, please feel free to let me know. Id probably use a LEFT JOIN, which will return rows even if theres no match, and then you can select only the rows with no match by checking for NULLs. This will return all rows including those where category does not exist in the other table. LEFT JOIN (SELECT *,'hello' AS Col1, 1 AS Col2 FROM A) t If you do not want to use a common table expression, you can choose to use a derived table (another table expression) instead, please refer to: SELECT B.*,t.Col1,t.Col2 You can tell number of rows in each table and whether Id in each table is Clustered Index or not. If inserted table contain less rows like 5,10 or even 20 then it will perform ok.
#Mysql join tables check for precence in a table code#
After TableA is defined, it can be referenced in any code afterwards. If you want to write same logic in UDF or Procedure then in place of inserted table you can use main table name like tbl1, tblM. TableA in your code is a common table expression, which is defined with with. The main function of table expressions is to construct various temporary data sets conveniently. It is a subquery in the form of a table, that is, a subquery is used instead of a table where it should be. Yes, for the same problem, many times TSQL can have multiple methods.įirst I want to explain that TableA is not an intermediate table, it is not even a real table.
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