sql server - Listing indexes and constraints - Database Administrators Stack Exchange
The database table I am looking at has a bigint NOT NULL column called id, yet, when I check for constraints, I don't see any, and the same holds true for all database tables
The problems with that technique are: 1) Only does a 1-direction compare; it doesn't tell you stuff in table2 that doesn't exist in table1, unlike the UNION technique 2) It doesn't handle NULLs in any of the columns, also unlike the UNION technique. So, I don't know which is faster (didn't test), but it is comparing apples to oranges, since they both return completely different results and the UNION technique gives you much more information from both tables and handles NULL gracefully
SQL Server Forums - Article: Calculating Running Totals
Within queries, this can be achieved by having one query return the first record, and if the record being executed is the first record, then it resets the stored value. This compares to about 7 seconds with the correlated subquery.As an aside, does anyone know if SQL Server will be adding analytic functions like Oracle has? This is a much better solution to this problem (performance wise)
SQL: Nulls: Nothing to Worry About
We can make a reasonable argument that SUM should return zero instead of null, that the sum of no values is zero, but Oracle's implementation of the behavior we describe here is fully compliant with the SQL standard. Apparently, if you want to derive the sum of two or more columns containing numeric values, there is a difference between first adding them up horizontally and then vertically, and adding them up vertically first
Sometimes a single query with 20 joins will perform just fine, and a query with 4 joins will actually perform better if split into steps that fill temp tables that are then joined. When you write new code, instead of using SELECT INTO, if you use a CREATE TABLE followed by INSERT SELECT, your code will be cloud-ready in this respect
SQL Server Engine Tips Using catalog views in SQL Server 2005 Posted over 9 years ago by SQL Server Engine Team 2 Comments Did you know that the catalog views in SQL Server 2005 exposes metadata for various objects in a database and at the server-level? This is the preferred method of accessing metadata. Posted over 9 years ago by SQL Server Engine Team 3 Comments Index Tuning Wizard (ITW in SQL Server 2000) or Database Engine Tuning Advisor (DTA in SQL Server 2005) allow you to analyze a workload and make recommendations for the database based on the workload
Dotnet Difference FAQs Blog
http://onlydifferencefaqs.blogspot.com/6 How to describe WCF services ? WCF SOAP services can be described in WSDL allowing automated tools to generate client proxies even for services with complex schemas. 10 When to go for WCF ? Choose WCF when we want to create a service that should support special scenarios such as one way messaging, message queues, duplex communication etc
Then check if the error is in the app code itself, or it this message is the result of catching a different error, and in the latter case find out what the original error was. Also, blogs are not really a good place for posting these questions; I suggest that you post your future questions to one of the many available online support forums on Internet
first i inserted 500.000 rows into a table with 5 columns: create table TestTable (col1 varchar(50), col2 varchar(50), col3 varchar(50), col4 varchar(50), col5 varchar(50)) in which for each 100k rows one column was filled with 50 chars and the rest were null. I'm not sure why that is, but I'm assuming it's a bug with STATISTICS TIME rather than an indication of performance, considering that the runtimes were identical
MySQL :: MySQL 5.0 Reference Manual :: 12.3.2 Comparison Functions and Operators
To comply with the SQL standard, IN returns NULL not only if the expression on the left hand side is NULL, but also if no match is found in the list and one of the expressions in the list is NULL. The arguments are compared using the following rules: If the return value is used in an INTEGER context or all arguments are integer-valued, they are compared as integers
Querying SQL Server 2012: Part II - CodeProject
8.1 CROSS APPLY The CROSS APPLY operator works like an INNER JOIN in that it can match rows from two tables and leaves out rows that were not matched by the other table in the result. The following query gets the top three most expensive orders regardless of customer and as a result each Person is duplicated three times in the result (once for each order, regardless of whether the order was placed by this Person)
Verify experience! Anyone considering using the services of an Oracle support expert should independently investigate their credentials and experience, and not rely on advertisements and self-proclaimed expertise
Adam Machanic : Performance: ISNULL vs. COALESCE
I ran these tests several times on a few different servers, and ISNULL appears to pretty consistently out-perform COALESCE by an average of 10 or 12 percent. He is a Microsoft Most Valuable Professional (MVP) for SQL Server, a Microsoft Certified IT Professional (MCITP), and an alumnus of the INETA North American Speakers Bureau
Therefore, the CASE expression looks like this: CASE WHEN NULL IS NOT NULL THEN NULL ELSE 0 END Try again, but this time using ISNULL instead of COALESCE: SELECT ISNULL( (SELECT SUM(col1) FROM dbo.T1), 0 ); This time you get the output 42. Can you explain how this could happen? In order to explain what happened, you need to examine the execution plan for the query in connection 2 shown in Figure 2
The ISNULL() function looks at the first value and the second parameter value is automatically limited to that length but COALESCE() does not have this restriction. Example declare @test varchar(3) select isnull(@test, 'ABCD') AS ISNULLResult select coalesce(@test, 'ABCD') AS coalesceResult OUTPUT In the above image, the test variable has length 3
This makes a difference if you are using these expressions in computed columns and creating key constraints or making return value of a scalar UDF deterministic so that it can be indexed
sql server - SQL - Difference between COALESCE and ISNULL? - Stack Overflow
USE tempdb; GO -- This statement fails because the PRIMARY KEY cannot accept NULL values -- and the nullability of the COALESCE expression for col2 -- evaluates to NULL. This makes a difference if you are using these expressions in computed columns, creating key constraints or making the return value of a scalar UDF deterministic so that it can be indexed as shown in the following example
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