Basic answer There are CTEs (Common Table Expressions) in Postgres – like in any major modern RDBMS, That includes MySQL since version 8.0. Since version 9.1 Postgres also features data-modifying CTEs, which can be “nested”. Unlike subqueries CTEs pose as optimization barriers. The query planner cannot inline trivial commands into the main command or reorder … Read more
select @code:= SUM(field1 + field2), @code+1 from abc; But, please be aware of the following (from the MySQL 5.6 docs): As a general rule, other than in SET statements, you should never assign a value to a user variable and read the value within the same statement. For example, to increment a variable, this is … Read more
That method doesn’t work in SQL Server. You can accomplish the same thing in a couple different ways: 1.) Use the code for each aliased column instead of the alias: (SELECT COUNT(*) FROM UserEvent UE WHERE UE.EventTypeID = 1 AND UE.PracticeID = au.PracticeID AND (UE.EventDate BETWEEN @Date1 and @Date2) – COUNT(CASE WHEN udi.DevicePlatform = ‘iOS’ … Read more
I think answer 4 is correct. There are a few considerations: type of subquery – is it corrrelated, or not. Consider: SELECT * FROM t1 WHERE id IN ( SELECT id FROM t2 ) Here, the subquery is not correlated to the outer query. If the number of values in t2.id is small in comparison … Read more
Based on the information in the article you linked to this should work: update giveaways set winner=”1″ where Id = (select Id from (select max(Id) as id from giveaways) as t)
Above example is not Co-related Sub-Query. It is Derived Table / Inline-View since i.e, a Sub-query within FROM Clause. A Corelated Sub-query should refer its parent(main Query) Table in it. For example See find the Nth max salary by Co-related Sub-query: SELECT Salary FROM Employee E1 WHERE N-1 = (SELECT COUNT(*) FROM Employee E2 WHERE … Read more
You need to alias the subquery. SELECT name FROM (SELECT name FROM agentinformation) a or to be more explicit SELECT a.name FROM (SELECT name FROM agentinformation) a
And for people who don’t quite get what the documentation is saying, a SUBQUERY is essentially this: SUBQUERY(collection, variableName, predicateFormat) And could (simplistically) be implemented like this: id resultingCollection = …; //a new collection, either a mutable set or array NSMutableDictionary * substitutions = [NSMutableDictionary dictionary]; NSPredicate * p = [NSPredicate predicateWithFormat:predicateFormat]; for (id variable … Read more
SELECT (sub)queries return result sets. So you need to use IN, not = in your WHERE clause. Additionally, as shown in this answer you cannot modify the same table from a subquery within the same query. However, you can either SELECT then DELETE in separate queries, or nest another subquery and alias the inner subquery … Read more
You want: insert into prices (group, id, price) select 7, articleId, 1.50 from article where name like ‘ABC%’; where you just hardcode the constant fields.