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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SQL Server's READ COMMITTED SNAPSHOT vs SNAPSHOT

I was researching the differences between SQL Server's READ COMMITTED SNAPSHOT and SNAPSHOT isolation levels and came across the following resource: Choosing Row Versioning-based Isolation Levels ...
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Database design: Dividing multiple identical tables, good or bad?

I am very new at SQL and databases in general. I only use them for the occasional homework so I haven't even tried to master them. I have seats at a theater, the seats are divided into 4 main areas ...
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2answers
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A good SQL sniffer

Can anyone point me to a good SQL sniffer where I can watch the SQL commands that run against my database in real time? If it's free, that would be great.
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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 ...
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Do SQL Server stored procedures cache data results?

I have heard this from friends, but I never investigated whether this is true. Is it true that the data results of an executed query are stored in cache? I mean, if I have a stored procedure like : ...
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Is there any difference between putting a column alias at the start or the end of the column definition?

I've always seen and written my column aliases as SELECT 1 as ColumnName but today came across a query that used SELECT ColumnName = 1 Is there any difference in how these two queries get ...
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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. ...
7
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2answers
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ORDER BY using custom priorities for text columns

This is a sample table: name | cat ---------- hugo | sal bob | mgr mike | dev jeff | mgr john | dev Both name and cat being Varchar. cat reflects a category for these names, but I like to assign ...
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4answers
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Combine column from multiple rows into single row

I've got some customer_comments split out into multiple rows due to database design, and for a report I need to combine the comments from each unique id into one row. I previously tried something ...
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votes
2answers
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How to do a case sensitive search in WHERE clause?

I want case sensitive search in SQL query. But by default, MySQL does not consider the case of the strings. Any idea on how to do a case sensitive search in SQL query?
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3answers
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What does the term “projection” refer to in an SQL query (or view definition)

In Oracle's document The Query Optimizer, under View Merging, I found the following information The view merging optimization applies to views that contain only selections, projections, and ...
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More Databases Per Sql Server 2005 Instance

Our company currently hosts about 400 databases per SQL Server 2005 instance. 500-600 databases and we see performance start to deteriorate. Database size ranges from 50mb to 40-60gb in the extreme, ...
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How to find parent rows that have indentical sets of child rows?

Suppose I have structure like this: Recipes Table: RecipeID Name Description RecipeIngredients Table: RecipeID IngredientID Quantity UOM What are some good ways for ...
7
votes
2answers
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What is the purpose of the USING parameter in SQL?

Working with some code on a standard MySQL database, and I came across this statement: SELECT * FROM foo LEFT JOIN bar USING ('bar_id') WHERE foo_id = 1 What's throwing me is: what is USING for, ...
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3answers
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SQL Calculated Field in both SELECT and GROUP BY clause

Often in querying my MS SQL Server databases, I need to create a calculated field, such as this (CASE WHEN A.type = 'Workover' THEN 'Workover' ELSE (CASE WHEN substring(C.category, 2, 1) = 'D' ...
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2answers
405 views

Where to start with Oracle?

This question only needs one answer: a list of great resources for getting started with Oracle, including Database Administration, PL/SQL and SQL. You may find your question has been closed as a ...
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4answers
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For a MySQL query, how do you determine physical and logical I/O?

I'm used to having a showplan in Microsoft SQL and have gotten lazy with using tools to tune MySQL queries. How can I determine physical/logical I/O for a query in MySQL? (EXPLAIN shows the index ...
7
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1answer
426 views

selecting where two columns are in a set

This might be a silly question, and my suspicion is that I can't do this, but is there a construct in SQL that would allow me to do something like the following: SELECT whatever WHERE col1,col2 IN ...
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3answers
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Why are NULLs sorted first?

Why is it that when we have a NULL value in a column and we order by the value ascending, the NULLs are sorted first? select 1 as test union all select 2 union all select NULL union all select 3 ...
7
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1answer
154 views

IN and NOT IN for XML column

I have a table with a xml column. Xml is similar to <Root> <Row> <user>abc</user> <Rowid>1</Rowid> </Row> <Row> ...
7
votes
1answer
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Algorithm for finding the longest prefix

I have two tables. First one is a table with prefixes code name price 343 ek1 10 3435 nt 4 3432 ek2 2 Second is call records with phone numbers number time 834353212 10 ...
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votes
2answers
358 views

Why do we have SHRINKDATABASE command in SQL Server

I have read across the internet where Finest Developer says shrinkdatabse should be avoided as it causes increase in fragmentation and decrease in performance . So i would like to know from you guys ...
7
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1answer
456 views

Adding SPARSE made table much bigger

I have a generic log table, about 5m rows. There's a "strongly typed" field that stores event type, and a bunch of "losely typed" columns that contain data relevant to the event. That is, meaning of ...
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4answers
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Multiple operations using WITH

Is there a way to execute multiple operations using the WITH statement? Something like WITH T AS ( SELECT * FROM Tbl ) BEGIN OPEN P_OUTCURSOR FOR SELECT * FROM T; SELECT COUNT(*) INTO ...
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3answers
2k views

Deleting all duplicates

I am trying to delete all the duplicates but keeping single record only (shorter id). Following query deletes duplicates but take lot of iterations to delete all copies and keeping original ones. ...
7
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3answers
5k views

How to Best Implement nearest neighbour search in mysql?

So, in short, What should be the data type of latitude and longitude? What SQL command I should call to get the first 100 nearest restaurants for example? Detail: I have 100k biz record each with ...
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How to effectively query and aggregate a normalized SQL db?

In relation to Most efficient way to return multiple aggregates in a single stored proc? I have an email type application and want to select all the messages (inbox) for a user. The problem is that I ...
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1answer
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Is it possible to limit the maximum disk usage for a user

Is it possible to set a limit on the amount of physical disk space a user (or group of users) can use within a single database? For example is there some method of associating a schema with a ...
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3answers
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SQL Server 2008 R2 High CPU

We are having a SQL Server R2 Web Edition database, based on Windows Server 2008 R2 with a strong CPU and 32GB RAM DDR3. Our database works very hard (we run around 600,000 queries in 1 minute) and ...
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votes
3answers
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Oracle's left join and where clauses errors

CREATE TABLE "ATABLE1" ( "COLUMN1" VARCHAR2(20 BYTE), "COLUMN2" VARCHAR2(20 BYTE) ); CREATE TABLE "ATABLE2" ( "COLUMN1" VARCHAR2(20 BYTE), "COLUMN2" VARCHAR2(20 BYTE) ); ...
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2answers
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Database behind a Multilingual User Interface

This question is about an issue somewhat more complicated than the one which has already been addressed in these old questions, all of which are duplicates of one another: Suggestion for database ...
7
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3answers
439 views

How to express this constraint in a database schema?

I have the following functional dependencies which are in BCNF: a,b -> c a -> d b -> d With the additional constraint, that no a and b should be combined with a c, where a and b have ...
7
votes
2answers
3k views

Database size - MDF too large?

I'm maintaining a SQL Server 2005 database which hosts approximately 2.9Tb of data (2 x 1.45Tb - I have a RAW schema and an ANALYSIS schema so basically two copies of the data ingested). The recovery ...
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2answers
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Oracle 11g: performance improvements of inserts

I have a table of 500 millions of rows (and growing) I did the following to improve performance of inserts: On database side: dropped all indexes and constraints disabled logging On application ...
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2answers
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PAGE compression in SQL Server effect on running queries

I am planning to apply PAGE compression to some of the big tables in my database (DW to be precise). These tables are fairly big with over 15 Billion rows. When I applied the compression in test ...
7
votes
4answers
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Select statement takes long remotely due to long “client processing time”, but short locally

While connected to our production server (SQL2008. very powerful machine), this select statement takes 2 seconds, spitting back all fields (4 MB of data in total). select top 30000 * from person ...
7
votes
2answers
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How to retrieve foreign key constraints data

I'm looking for a query allowing to retrieve foreign key infos (each line: referrencing table & field, referrenced table & field) of an entire schema. I've found this, but does not gives all ...
7
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1answer
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T-SQL - OPTION (FAST x) and trace flag 8722

I have searched a long time and still haven't found the answer to my problem. Our Dynamics AX is generating queries with the query hint OPTION (FAST x), which sometimes forces a bad execution plan to ...
7
votes
1answer
256 views

Table order in Join Query

if i say: Table1 left join Table2 is it the same as saying Table2 right join Table1 ? In other words, should i expect to get the same results from 2 identical queries where the only thing that is ...
7
votes
4answers
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How do I do a complex GROUP BY in MySQL?

I have a table that contains several keys into other tables (where each key is comprised of multiple columns). I would like to be able to group rows together that have an equal key, but I don't want ...
7
votes
1answer
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Is the optimisation fence behaviour of a CTE (WITH query) specified in the SQL:2008 standard? If so, where?

I see frequent references to WITH queries (common table expressions, or CTEs) acting as an optimisation fence, where the server isn't permitted to push filters down into the CTE queries, pull common ...
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6answers
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SQL Query Formatter [closed]

Are there any (Linux based) SQL Query Formatting programs/plugins/extensions? I use PostgreSQL and MySQL but other DB's are welcome as well. I can use a VM to test with but would prefer a Linux ...
7
votes
5answers
15k views

Error 3154 while restoring a backup using WITH REPLACE

I have SQL 2012 with SP1 installed on my computer. I made a backup of a database test.bak. I have a database with the name test2 which is the same database, but the data changed. I want to restore ...
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2answers
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SQL Server backup failing. Error: 3041, Severity: 16, State: 1

First of all, I'm very new at stackexchange, so please bear with me. I'm running a SQL Server 9.0.4060. My problem is: my SQL Server backup keeps failing on a lot of the databases. The Maintenance ...
7
votes
1answer
86 views

sysschedules datatype choices

I am Curious. Why does TSQL save the values in msdb.dbo.sysschedules for date and times as ints instead of using datetime. I assume the reason dates back to something in SQL Server 2000. Was it a ...
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6answers
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Maximum value from multiple tables

Consider the following situation: we have T1, T2, & T3 tables in which saved id and price of products. Now we need to find the id of products which have maximum price of all 3 tables. I have this ...
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2answers
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Using wildcards in a like statement on an unindexed VARCHAR(MAX) column with more than 1 million records

In order to troubleshoot a problem, I have a one-time question as to whether a specific varchar(max) field contains non-printing ASCII characters (other than white-space). The following is my ...
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2answers
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Convert units of measurement

Looking to calculate the most suitable unit of measurement for a list of substances where the substances are given in differing (but compatible) unit volumes. Unit Conversion Table The unit ...
7
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2answers
6k views

SQL Server: query performance (search 2 million rows)

Got an interesting one for all of you SQL guru's out there. Now this search is only taking a couple of seconds, but it's quite intensive and there must be a better way. Maybe I'm expecting too much? ...
7
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1answer
100 views

Is there a performance hit by breaking out tables into different schemas in SQL Server?

Is there any kind of performance hit when querying by placing tables in different schemas in SQL Server. For instance if I had 2 tables, Table1 and Table2, and put Table1 into the test schema and ...