sql standard - Database Administrators Stack Exchange
2018年10月31日 · In general terms, a clause is just a logical chunk of a SQL statement - and, usually, is a chunk that is (theoretically) optional. I'm a SQL Server guy, so I'll be thinking in those terms. SELECT GETDATE() is a valid SQL Server SELECT statement. It'll return the current date and time. If I add a FROM clause: SELECT GETDATE() FROM sys.objects
sql server - Merge two SELECT queries with different WHERE …
2014年4月19日 · I have one table of services. I need to merge two SELECT queries. Both have different where clauses. For example SELECT U_REGN as 'Region', COUNT(callID) as 'OpenServices', SUM(CASE WHEN
Steps or evaluation order of the SQL statement
2014年11月5日 · How the SQL statement containing simple statement like Select x From y Where z Having, order by , group by etc. are evaluated.
mysql - Database Administrators Stack Exchange
2018年2月18日 · Stack Exchange Network. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
sql server - order of clauses in "EXISTS (...) OR EXISTS ...
2017年4月12日 · That effectively forces SQL Server to run the subquery against the table with a clustered index first. Here are the results from SET STATISTICS IO, TIME ON: Table 'X_CI'. Scan count 0, logical reads 3, physical reads 0. SQL Server Execution Times: CPU time = 0 ms, elapsed time = 0 ms.
Is there any limit for IN results in SQL Server?
2019年2月1日 · This issue occurs because SQL Server limits the number of identifiers and constants that can be contained in a single expression of a query. This limit is 65,535. 32767 works and 32768 doesn't work.
sql server - Logical operators OR AND in condition and order of ...
How SQL Server short-circuits WHERE condition evaluation. It does when it feels like it, but not in the way you immediately think of. As a developer you must be aware that SQL Server does not do short-circuiting like it is done in other programming languages and …
SQL optional where clauses without exponentially large number of …
2020年5月14日 · For 2 clauses and 3 options, we have 3^2 = 9 different queries to write. If we add another 1-2 where clauses, this quickly becomes overwhelming and duplicates a lot of code for what is effectively the same problem.
sql server - Where clause for aliased column - Database …
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Optimizing large MySQL SELECT WHERE IN clauses
I have had success in general replacing lengthy IN operations with a join against a temporary table. This makes sense because RDBMS are optimized to perform JOIN's as efficiently as possible, and the handling of lengthy IN lists will most likely be done by repeating the query for every value in the IN list.