DO NOT USE this for questions targeting Microsoft SQL Server, use the tag sql-server instead. "SQL" is an acronym for "Structured Query Language", it is used in relational database management systems (RDBMS) to query, update, delete, and insert data as well as modify the structure of the database. ...

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2answers
6k views

Best way to populate a new column in a large table?

We have a 2.2 GB table in Postgres with 7,801,611 rows in it. We are adding a uuid/guid column to it and I am wondering what the best way to populate that column is (as we want to add a NOT NULL ...
12
votes
1answer
849 views

How can I design a query to pause / sleep / wait for a specified amount of time?

I am testing a monitoring application against a SQL Server 2000 instance. How can I write a T-SQL query that takes an amount of time that I specify? For example, most scripting languages have ...
12
votes
1answer
2k views

Patterns for setting up sharding for SQL Server 2008 R2, in order to handle large datasets?

I want to handle a large dataset (> 1 billion rows) in SQL Server 2008 R2. I heard that if you set up "sharding" or "horizontal partitioning", it makes it quicker to handle large datasets as it breaks ...
12
votes
2answers
650 views

Decision criteria on when to use a non-dbo schema vs a new Database

I'm mostly an application developer but find myself having to do all the up-front database work for my current project (btw... its MS SQL Server 2008). As a first decision, I'm trying to figure out ...
12
votes
4answers
1k views

Creating centralized DBA database

We have 200+ servers and I am thinking about creating a centralized DBA database where it logs backup, errors, space jobs and generate reports on SSRS. I am not sure where to start and I would highly ...
12
votes
1answer
3k views

Why does NOT IN with a set containing NULL always return FALSE/NULL?

I had a query (for Postgres and Informix) with a NOT IN clause containing a subquery that in some cases returned NULL values, causing that clause (and the entire query) to fail to return anything. ...
12
votes
5answers
4k views

Efficiently select beginning and end of multiple contiguous ranges in Postgresql query

I've got about a billion rows of data in a table with a name and an integer in the range 1-288. For a given name, every int is unique, and not every possible integer in the range is present--so there ...
12
votes
2answers
30k views

How to pass in parameters to a SQL Server script called with sqlcmd? [closed]

Is it possible to pass parameters to a SQL Server script? I have a script that creates a database. It is called from a batch file using sqlcmd. Part of that SQL script is as follows: CREATE DATABASE ...
12
votes
1answer
346 views

Why does subquery use parallelism and join doesn't?

Why does SQL server use parallelism when running this query which uses a subquery but it doesn't when using a join? The join version runs in serial and takes around 30 times longer to complete. Join ...
12
votes
1answer
9k views

Order by column should have index or not?

I have added indexes to table which are used for searching result. I am showing results by ASC or DESC order. So that column should have index or not? I have 2 more indexes on that table. How ...
12
votes
2answers
169 views

What programming language is this?

:#PCA=Campaign//CampId//CampDesc//CampBusId = 2 :#PE=PubEdition//EdId//EdCode//EdCampId = :#PCA :#PCT=ContactType//ContTypeCd//ContTypeDesc//ContTypeUsrId in (21, 25) ...
12
votes
3answers
6k views

Best way to design tournament database

I'm creating a webpage for placing bets on all matches of the upcoming Euro 2012 football tournament. Need some help deciding what approach to take for the knockout phase. I have created a mockup ...
12
votes
2answers
2k views

Fastest way to change a 600GB table indexed key datatype from INT to BIGINT

I need to change a datatype from INT to BIGINT in a 600GB MySQL table. The column has a unique index. I might be good with unsigned INT, but I assume changing to that or BIGINT will be pretty much ...
12
votes
2answers
566 views

SQL Server 2008 Performance issue with very strange resolution

I'm a long time DBA (12 years in SQL). I'm running SQL Server 2008 Enterprise in a Win 2008 clustered environment. 128gb memory and 32cpu in each cluster node. Not wimpy. I've got the weirdest ...
11
votes
3answers
11k views

Are individual queries faster than joins?

Conceptual question: Are individual queries faster than joins, or: Should I try to squeeze every info I want on the client side into one SELECT statement or just use as many as seems convenient? ...
11
votes
3answers
520 views

Can IS DISTINCT FROM be combined with ANY or ALL somehow?

Is a postgres way of combining IS DISTINCT FROM with ANY or some other neat way of getting the same result? select count(*) from (select 'A' foo union all select 'Z' union all select null) z where ...
11
votes
3answers
5k views

Should I use SQL JOIN or IN Clause?

I have a question about best approach. I am not sure which approach is best when data is considered variable in size. Consider the following 3 TABLES: EMPLOYEE EMPLOYEE_ID, EMP_NAME PROJECT ...
11
votes
1answer
4k views

Postgres Update, limit 1

I have a postgres database which contains details on clusters of servers, such as server status (active, standby, etc). Active servers at any time may need to fail over to a standby, and I don't care ...
11
votes
2answers
58k views

Oracle: Quick way to list all database links

The title says it all, is there a way to quickly list all the current database links in oracle? Something along the same lines as this, which lists the current user's tables: select * from ...
11
votes
2answers
1k views

Optimization: Moving variable declarations to the top of your procedure

While working on optimizing some stored procedures, I sat down with the DBA and went through some sprocs with high blocking and/or high read/write activity. One thing the DBA mentioned was I should ...
11
votes
1answer
12k views

Performance implications of using OPENQUERY in a view

Please see this question on stackoverflow : I am using an EasySoft ODBC driver to link a SQL Server 2008 R2 Express instance to Interbase and I am having some difficulty with getting metadata ...
11
votes
2answers
4k views

Does MySQL cache queries?

I'm interfacing a MySQL database with PHP Data Objects (PDO) and executing an extensive SQL query. Normally, it takes about 1500 ms; I still need to optimize it. When I run the PHP script twice ...
11
votes
3answers
2k views

Updating a table with millions of records, its been 4 days

I am currently updating a table with millions of records, its been 4 days and query is still executing. I checked the activity monitor its shows that query is running. In event log there is no ...
11
votes
2answers
5k views

Reasons for occasionally slow queries?

We are running MySQL 5.1 on Windows Server 2008 R2. We have been doing some diagnostics on our database of late and have found some disturbing artifacts which we can't explain. We added some code to ...
11
votes
3answers
4k views

Choosing a database for storing large amount of data and allowing for thousands of writes [closed]

I am working on a project that has some serious requirements regarding its database and having hard time choosing the best solution. The details are: Database will easily reach tens of terabytes of ...
11
votes
3answers
7k views

Why is an aggregate query significantly faster with a GROUP BY clause than without one?

I'm just curious why an aggregate query runs so much faster with a GROUP BY clause than without one. For example, this query takes almost 10 seconds to run SELECT MIN(CreatedDate) FROM MyTable WHERE ...
11
votes
3answers
1k views

Use MySQL to regularly do multi-way joins on 100+ GB tables?

Background: I’ve created a web application that I would like to be able to scale reasonably well. I know I'm not Google or Twitter, but my app uses a fairly large amount of data for each user and thus ...
11
votes
3answers
2k views

Why does my ORDER BY sort two tables before the EXCEPT (slow) and not after (fast)?

SQL server 2008 R2 query optimizer puzzle We have two tables, both containing 9 million rows. 70.000 rows are different, the others are the same. This is fast, 13 seconds, select * from bigtable1 ...
10
votes
4answers
4k views

Benefits of using backtick (`) in MySQL queries?

In MySQL we can create queries with or without the backtick (`) symbol. Example: SELECT * FROM TEST; SELECT * FROM `TEST`; Both works fine in mysql-console. Is there any technical difference ...
10
votes
3answers
6k views

CHECKPOINT or COMMIT writes to disk?

Let's say, for SQLServer2008R2 and higher, with full recovery mode databases. I always thought : When a transaction is commited (COMMIT), the transaction is written to the transaction log in RAM. ...
10
votes
1answer
429 views

how do I insert a default row?

If I create a table with an identity column as primary key, and all the other columns have default values, for example create table rr (id int identity(1,1) primary key, dt datetime default ...
10
votes
3answers
15k views

Notification on long-running query or deadlock in SQL Server 2008 R2?

I'd like to know if there is a way to send a notification on deadlock? If so what queries would be required. I understand that SQL Server takes care of deadlocks, I simply would like information on ...
10
votes
2answers
777 views

Postgres query plan of a UDF invocation written in pgpsql

It's possible when using the pgadmin or plsql to get a hold of a query plan for a sql statement executed via a UDF (using EXPLAIN). So, how do I get a hold of the query plan for a particular ...
10
votes
2answers
38k views

Returning a result set with multiple rows based on max date

I have a child table that is something like this: [Cust Date Table] | Customer ID | Some Date | Balance | +-------------+------------+---------+ | 1 | 2012-04-30 | 20.00 | | 1 ...
10
votes
1answer
4k views

Deadlock error isn't returning the deadlock SQL

Transaction (Process ID) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction. I am getting this error randomly when one of my ...
10
votes
3answers
172 views

Combining separate ranges into largest possible contiguous ranges

I'm trying to combine multiple date ranges that may or may not overlap into the largest possible contiguous date ranges. For example: Data: CREATE TABLE test ( id SERIAL PRIMARY KEY NOT NULL, ...
10
votes
1answer
216 views

Rejoining range seek on nullable composite index?

For the following schema and example data CREATE TABLE T ( A INT NULL, B INT NOT NULL IDENTITY, C CHAR(8000) NULL, UNIQUE CLUSTERED (A, B) ) INSERT INTO T (A) ...
10
votes
1answer
3k views

How to preserve the original order of elements in an unnested array?

Given the string: 'I think that PostgreSQL is nifty' I would like to operate on the individual words found within that string. Essentially, I have a separate from which I can get word details ...
10
votes
2answers
6k views

Create View in specified database with dynamic sql?

I am writting a dynamic sql to drop and create view in different database. So I wrote: set @CreateViewStatement = ' USE ['+ @DB +']; CREATE VIEW ...
10
votes
5answers
9k views

Use of HAVING without GROUP BY in SQL queries

In order to use HAVING in SQL queries , must there be a GROUP BY to aggregate the column names? Are there any special cases where it is possible to use HAVING without a GROUP BY in SQL queries? ...
10
votes
1answer
2k views

Generate an exception with a Context

When PostgreSQL throws an exception, there is a line "CONTEXT" like: ERROR: INSERT has more target COLUMNS than expressions LINE 3: ... ...
10
votes
3answers
3k views

Database starts always in recovery mode

Everytime I restart my server, the database is always in recovery mode, and it takes about 20 minutes for it to behave as normal. This always and only happens when I restart the server, so I have a ...
10
votes
4answers
3k views

Table partitioning for archiving data

Scenario: two databases: DB_A and DB_Archive with one very big table called tableA. every day, records older than 60 days are deleted from DB_A and moved to DB_Archive mainly to leave thing ...
10
votes
2answers
173 views

Find total duration of each consecutive series of rows

MySQL Version The code will run in MySQL 5.5 Background I have a table like the following one CREATE TABLE t ( id INT NOT NULL AUTO_INCREMENT , patient_id INT NOT NULL , bed_id INT NOT NULL , ...
10
votes
1answer
17k views

Stored Procedure to return dynamically created table data

Quick back story, we are working with an outside vendor that has a survey system. The system is not necessarily designed the best in that when you create a new survey and the system creates a new ...
10
votes
1answer
512 views

Resolving deadlock from 2 tables only related through indexed view

I have a situation where I'm getting deadlocks, and I think I've narrowed down the culprits, but I'm not quite sure what I can do to fix it. This is on a production environment running SQL Server ...
9
votes
3answers
66k views

How do I insert a row which contains a foreign key?

Using PostgreSQL v9.1. I have the following tables: CREATE TABLE foo ( id BIGSERIAL NOT NULL UNIQUE PRIMARY KEY, type VARCHAR(60) NOT NULL UNIQUE ); CREATE TABLE bar ( id BIGSERIAL ...
9
votes
3answers
504 views

Are these two queries logically equivalent?

Are these two queries logically equivalent? DECLARE @DateTime DATETIME = GETDATE() Query 1 SELECT * FROM MyTable WHERE Datediff(DAY, LogInsertTime, @DateTime) > 7 Query 2 SELECT * FROM ...
9
votes
6answers
437 views

Backing up SQL DB more frequently

I currently have a scheduled task that fires off each night at 2 AM that calls SQLCMD.exe and passes it a .sql script to run for the backup (shown below). We're a pretty small company with growing ...
9
votes
3answers
8k views

How do you clear out all old query plans from within Microsoft SQL Server?

We have an off the shelf application that uses a Microsoft SQL database. Within this application we pick and choose various selection criteria for each report. This application then runs these ...