Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [sql-server]

All versions of Microsoft SQL Server (not MySQL). Please also add a version-specific tag, like sql-server-2016, since it is often relevant to the question.

32
votes
2answers
12k views

Optimising plans with XML readers

Executing the query from here to pull the deadlock events out of the default extended events session SELECT CAST ( REPLACE ( REPLACE ( XEventData.XEvent.value ('(data/value)[...
32
votes
5answers
27k views

Handling concurrent access to a key table without deadlocks in SQL Server

I have a table that is used by a legacy application as a substitute for IDENTITY fields in various other tables. Each row in the table stores the last used ID LastID for the field named in IDName. ...
32
votes
2answers
57k views

Which one is more efficient: select from linked server or insert into linked server?

Suppose I have to export data from one server to another (through linked servers). Which statement will be more efficient? Executing in source server: INSERT INTO [DestinationLinkedServer].[...
32
votes
1answer
64k views

How do I attach a database in SQL Server?

Some common questions relating to attaching databases in SQL Server: What does it mean to attach or detach a database? How do I detach a database? How do I attach a database? What ...
32
votes
2answers
43k views

ISO Week vs SQL Server Week

Okay so I have a report that does a this week vs last week comparison and our customer noticed that their data was "funky". Upon further investigation we found it was not doing weeks correctly ...
32
votes
5answers
109k views

Logical operators OR AND in condition and order of conditions in WHERE

Let's examine these two statements: IF (CONDITION 1) OR (CONDITION 2) ... IF (CONDITION 3) AND (CONDITION 4) ... If CONDITION 1 is TRUE, will CONDITION 2 be checked? If CONDITION 3 is FALSE, will ...
31
votes
8answers
2k views

Security implications of restoring a backup from an unknown source?

Scenario: You're handed a database backup and told to restore it to a server (that's already hosting other databases), but are given no useful information about what the backup contains or whether the ...
31
votes
5answers
180k views

Why is SQL Server consuming more server memory?

SQL Server is consuming 87.5 % of my server RAM. This recently caused a lot of performance bottlenecks such as slowness. I researched this issue. One common solution I could find on the internet is to ...
31
votes
1answer
5k views

DBA first day in a new job - check backups and security - How? what else should be checked?

Generally when I start in a new environment, I tend to check where are the backups, when the last full was taken, when was the last restore applied and I check the security too. The way I do this is ...
31
votes
2answers
8k views

Does the order of columns in a PK index matter?

I have a few very large tables with the same basic strucure. Each one has a RowNumber (bigint) and DataDate (date) column. Data is loaded using SQLBulkImport every night, and no "new" data is ever ...
31
votes
3answers
7k views

Why would a SELECT query cause writes?

I've noticed that on a server running SQL Server 2016 SP1 CU6 sometimes an Extended Events session shows a SELECT query causing writes. For example: The execution plan shows no obvious cause for the ...
31
votes
2answers
6k views

Why does query error with empty result set in SQL Server 2012?

When running the following queries in MS SQL Server 2012 the second query fails but not the first. Also, when run without the where clauses both queries will fail. I am at a loss why either would fail ...
31
votes
4answers
5k views

Why does SQL Server return some rows while still executing the query, and sometimes not?

There are queries where when we hit "execute", it shows some rows and it keeps growing, but the query is not over yet. Yet sometimes, it waits until the end of the query. Why does this happen? Is ...
31
votes
1answer
48k views

Cannot execute as the database principal because the principal “dbo” does not exist [duplicate]

I restored a backup of a database from SQL Server 2008 R2 to SQL Server 2012. When I try to access a particular page of my application, I get this error: Cannot execute as the database principal ...
31
votes
3answers
27k views

For absolute performance, is SUM faster or COUNT?

This relates to counting the number of records that match a certain condition, e.g. invoice amount > $100. I tend to prefer COUNT(CASE WHEN invoice_amount > 100 THEN 1 END) However, this is ...
31
votes
3answers
8k views

What are valid usage scenarios for HEAP tables?

I am currently doing some data imports into a legacy system and discovered that this system does not use a single clustered index. A quick Google search introduced me to the concept of HEAP tables and ...
31
votes
1answer
3k views

Very strange performance with an XML index

My question is based on this: https://stackoverflow.com/q/35575990/5089204 To give an answer there I did the following test-scenario. Test scenario First I create a test table and fill it with 100....
31
votes
1answer
1k views

Why is the speed of executing statements dependent on the network connection?

It looks like the speed of executing T-SQL is dependent on the latency of the network connection against the server. I assumed that if SQL Server has nothing to report back to the client about, it ...
31
votes
3answers
46k views

What is the difference between Shrink Database and File?

DBCC ShrinkDatabase() DBCC ShrinkFile() Do I need to run both DBCC commands in order to shrink the database? What is the difference between these two above?
31
votes
3answers
36k views

Is the SQL Server Express memory and CPU limit per instance?

If I have 8GB of RAM in a server and I run 4 instances of SQL Server Express, will the total memory limit used by SQL Server be 1GB or 4GB? Would it be advisable to run multiple instances like this ...
31
votes
2answers
2k views

Where can I find database tuning exercises for learning?

As a developer, often DBAs take responsibility for resolving performance issues at the database level so we don't get that much experience diagnosing, tuning, refactoring queries etc. I'm looking ...
31
votes
1answer
13k views

Setting BUFFERCOUNT, BLOCKSIZE, and MAXTRANSFERSIZE for BACKUP command

I am looking for practical guidance for setting the values for the BUFFERCOUNT, BLOCKSIZE, and MAXTRANSFERSIZE of the BACKUP command. I have done a bit of research (see below), I have done a bit of ...
30
votes
2answers
123k views

Best way to get last identity inserted in a table

Which one is the best option to get the identity value I just generated via an insert? What is the impact of these statements in terms of performance? SCOPE_IDENTITY() Aggregate function MAX() ...
30
votes
7answers
108k views

IntelliSense not working but it is enabled

This problem is really proving to be a tricky one (and quite annoying). In SQL Server Management Studio 2008, up until a few days ago my IntelliSense was working great. Then all of a sudden it ...
30
votes
2answers
8k views

How to make a transition from SQL Server DBA to Oracle?

As an interest, if I would to transition from a SQL Server DBA to Oracle what will be the major learning or unlearning that I would have to do? I would assume the concepts are the same and the ...
30
votes
4answers
14k views

CPU clock speed versus CPU core count - higher GHz, or more cores for SQL Server?

We are beginning to provision a set of physical servers for a virtual cluster of SQL Server 2016 nodes within VMware. We will be utilizing Enterprise Edition licenses. We plan on setting up 6 nodes, ...
30
votes
6answers
50k views

Load Balancing with SQL Server

What exists today to do Microsoft SQL Server Load Balancing on Windows Server and being transparent to any programmatic access. Is this built in or does a solution have to be purchased? I'm trying to ...
30
votes
5answers
8k views

Why use an int as a lookup table's primary key?

I want to know why I should use an int as a lookup table's primary key instead of just using the lookup value as the primary key (which in most cases would be a string). I understand that using a ...
30
votes
2answers
56k views

Outer Apply vs Left Join Performance

I am Using SQL SERVER 2008 R2 I just came across APPLY in SQL and loved how it solves query problems for so many cases, Many of the tables I was using 2 left join to get the result, I was able to ...
30
votes
7answers
51k views

What is the most efficient way to get the minimum of multiple columns on SQL Server 2005?

I'm in a situation where I want to get the minimum value from of 6 columns. I've found three ways so far to accomplish this, but I have concerns with the performance of these methods and would like ...
30
votes
6answers
31k views

SQL Server compatibility with New TLS Standards

The major browsers are moving beyond SSL3.0 and TLS1.0 . The PCI Security Council has declared an end-of-life date for these protocols to be considered sufficiently strong encryption. We need to move ...
29
votes
4answers
804 views

What is a scalable way to simulate HASHBYTES using a SQL CLR scalar function?

As part of our ETL process, we compare rows from staging against the reporting database to figure out if any of the columns have actually changed since the data was last loaded. The comparison is ...
29
votes
1answer
3k views

How does SQL Server determine key column order in missing index requests?

How does SQL Server determine the order of key columns in its missing index recommendations for a query plan?
29
votes
2answers
41k views

How do I drop all constraints from all tables?

I want to drop all default constraints, check constraints, unique constraints, primary keys and foreign keys from all tables in a SQL Server database. I know how to get all the constraint names from ...
29
votes
4answers
27k views

How do I identify the column(s) responsible for “String or binary data would be truncated.”

I am generating some queries automagically with code I wrote to SELECT from a remote Pg database, and insert into a local SQL Server database. However, one of them is generating this error: [...
29
votes
1answer
2k views

What are Objective Reasons to Prefer SQL Server 2016 over Earlier Versions?

As Microsoft makes SQL Server version upgrades more frequently since the SQL Server 2005 or 2008 days, a lot of companies find it difficult to determine when an upgrade is a "must have!" and when an ...
29
votes
1answer
2k views

Why is a scan faster than seek for this predicate?

I was able to reproduce a query performance issue that I would describe as unexpected. I'm looking for an answer that's focused on internals. On my machine, the following query does a clustered index ...
29
votes
4answers
7k views

LocalDB v14 creates wrong path for mdf files

Recently, I upgraded LocalDB from version 13 to 14 using the SQL Server Express installer and this instruction. After the installation, I stopped the existing default instance (MSSQLLOCALDB) of ...
29
votes
3answers
9k views

Which PowerShell technique should I use to talk to SQL Server?

I'd ultimately like to use PowerShell to replace the old KornShell scripts we use for SQL instance monitors. I'm having a hard time, though, getting my brain around all the different ways that ...
29
votes
5answers
3k views

SQL Deadlock on the same exclusively locked clustered Key (with NHibernate) on delete / insert

I have been working on this deadlock issue for quite a few days now and no matter what I do, it persists in one way or another. First, the general premise: We have Visits with VisitItems in a one to ...
28
votes
8answers
38k views

How to query a database for empty tables

Due to some 'developers' we had working on our system we have had issues with empty tables. We have found that during the transfer to the cloud several tables were copied, but the data in them wasn't....
28
votes
5answers
191k views

How to handle TimeZone properly in SQL Server?

My local development server is in the Middle East, but my production server is in the UK. I need to show the date to the user in their time zone. For example, if a user is in Saudi Arabia then I ...
28
votes
3answers
3k views

Why does SQL Server use a better execution plan when I inline the variable?

I have a SQL query that I am trying to optimize: DECLARE @Id UNIQUEIDENTIFIER = 'cec094e5-b312-4b13-997a-c91a8c662962' SELECT Id, MIN(SomeTimestamp), MAX(SomeInt) FROM dbo.MyTable WHERE Id = @...
28
votes
2answers
12k views

Why do wildcards in GROUP BY statements not work?

I am trying to make the following SQL statement work, but I get a syntax error: SELECT A.*, COUNT(B.foo) FROM TABLE1 A LEFT JOIN TABLE2 B ON A.PKey = B.FKey GROUP BY A.* Here, A is a wide table with ...
28
votes
3answers
23k views

Adding columns to production tables

What's the best way to add columns to large production tables on SQL Server 2008 R2? According to Microsoft's books online: The changes specified in ALTER TABLE are implemented immediately. If the ...
28
votes
9answers
2k views

What is the most efficient method of performing the FIZZBUZZ test in SQL Server?

This may not be completely on-topic, however it's a slow day here. Is there a more efficient method of obtaining a list of numbers from 1 to 49 with a column containing the words FIZZ when the number ...
28
votes
2answers
9k views

If positive, sum all items. If negative, return each one

I am needing to find a way to SUM() all of the positive values for num and return the SUM() of all positive numbers and an individual row for each negative number. Below is a sample DDL: Create ...
28
votes
3answers
6k views

When are computed columns computed?

When are the values for computed columns determined? When the value is retrieved? When the value is changed? Some other time? I'm guessing this is a novice question since I'm not finding anything in ...
28
votes
2answers
10k views

Using indexed views for aggregates - too good to be true?

We have a data warehouse with a fairly large record count (10-20 million rows) and often run queries that count records between certain dates, or count records with certain flags, e.g. SELECT f....
28
votes
19answers
36k views

SQL Server Management Studio slow opening new windows

After upgrading both SQL Server and Management Studio from 2008 to 2012, Management Studio 2012 is very slow when new query windows and dialog boxes are opened. Even right clicking on tables is slow. ...