Structured Query Language (SQL). For questions about the language, not Microsoft SQL Server (tag sql-server).

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Learning to Optimize SQL Queries and Understand Execution Plans - Resources?

I find myself writing more and more SQL queries at work (mostly Oracle 11g, but some SQL Server 2005-2008) and have started creating some pretty complex views for the rest of the analyst team. They ...
5
votes
2answers
7k views

Prevent copying to temp table (sql)

I have two tables - comments and votes : comments(id, text, user_id, page_id) votes(id, value) There are 2,000,000 rows in the votes table. I created the following query: SELECT ...
5
votes
4answers
5k views

MySQL: Index when joining to tables not being used (Performance optimizing question)

I need to optimize the following query: SELECT /* [things omitted] */ articles.blogpost_id, articles.id AS articleid FROM blogposts JOIN articles ON articles.blogpost_id = blogposts.id WHERE ...
22
votes
5answers
16k views

Can I add a unique constraint that ignores existing violations?

I have a table which currently has duplicate values in a column. I cannot remove these erroneous duplicates but I would like to prevent additional non-unique values from being added. Can I create a ...
8
votes
5answers
3k views

Why is the SELECT clause listed first? [closed]

I'm not sure if this question is on-topic - if not, feel free to close. Also, if it'd be a better question for another StackExchange site, I can ask it elsewhere. I was wondering why SQL places the ...
5
votes
3answers
14k views

How to model inheritance of two tables mysql

I have some tables where I store data and depending on the type of person (worker,civil) that did a job I want to store it a table 'event', now these guys rescue an animal (thereis a table animal). ...
5
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4answers
15k views

Building Dynamic Oracle Where Clause

I'm working on application that uses dynamic query to do a select statement based on user input, after discussing security with DBAs they want me to convert my dynamic select statement into Stored ...
2
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2answers
372 views

SQL Backup tuning large databases

I am tuning SQL backups using compression, writing to multiple files, and changing the BufferCount and MaxTransferSize options. I have SQL instance with a 4 TB database and several smaller databases ...
12
votes
4answers
4k views

Is it possible to increase query performance on a narrow table with millions of rows?

I have a query that is currently taking an average of 2500ms to complete. My table is very narrow, but there are 44 million rows. What options do I have to improve performance, or is this as good as ...
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votes
6answers
7k views

Find “n” consecutive free numbers from table

I have some table with numbers like this (status is either FREE or ASSIGNED) id_set number status ----------------------- 1 000001 ASSIGNED 1 000002 FREE 1 000003 ...
8
votes
3answers
4k views

How can I improve my SQL statement with weekly results with week starting on Thursday or any other day of the week?

I am a total newb, and I couldn't find a good way to do this anywhere. I have a database table that contains statistics that are recorded at various time throughout the week. The reporting week ...
7
votes
2answers
4k views

What are the differences between SQL I/O Sim and SQL IO tools?

I want to test my different SQL Server alternatives with a benchmark tool. I found two tools by Microsoft: SQLIO Disk Subsystem Benchmark Tool SQL IO Sim What are the differences between them? is ...
5
votes
2answers
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What is the meaning of tinyint(N)?

When we use an argument length with numerical data types, as far as I know this specifies the display width. I tried the following: mysql> create table boolean_test (var1 boolean, var2 tinyint); ...
5
votes
2answers
5k views

PostgreSQL query with max and min date plus associated id per row

I have the following table: CREATE TABLE trans ( id SERIAL PRIMARY KEY, trans_date date, trans_time time ); I want to have the following view CREATE OR REPLACE VIEW daily_trans ...
4
votes
1answer
576 views

Pull data from multiple tables in a view or function

There are 3 tables from which I need to pull data, and print it in a specific way. http://sqlfiddle.com/#!15/59481/8 Refer to this question to see how the query was produced. The version in the ...
3
votes
2answers
2k views

PostgreSQL joining using JSONB

I have this SQL: CREATE TABLE test(id SERIAL PRIMARY KEY, data JSONB); INSERT INTO test(data) VALUES('{"parent":null,"children":[2,3]}'); INSERT INTO test(data) ...
3
votes
2answers
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Database design for an E-commerce website

I am new to database design. I am designing a database for an E-commerce website, there are a lot of products to be updated, but while designing for product specification table I do not understand ...
2
votes
3answers
39k views

SQL Update column with data from another table

I am working on complicated problem, but I will simplify it to this problem. I have two tables A [ID, column1, column2, column3] B [ID, column1, column2, column3, column4] and i want to update ...
2
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3answers
3k views

SQL Subquery , One to Multiple rows

Following query I have written returns the result as expected, example 121350 rows. SELECT dbo.Articles_in_Consignment.Consignment_id, dbo.ORDER_D.Orders_boxsize, ...
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2answers
906 views

Tsql Query speed slow due to Or within where clause, causing index scan instead of seek

I have been working on making this query work more efficiently. I found that the number of Ors within the where clause are the biggest problem within this query. This query sits in a stored ...
-2
votes
4answers
3k views

Is there a SELECT statement to subtract rows of the same column?

Column 1 is the mem_id, Column 2 is the Transaction type C and D, and Column 3 is the Amount Owed. So I want to return Column 3 "Amount Owed", but it has to be C-D in Column 2 for each member. ...
27
votes
4answers
9k views

Performance difference for COALESCE versus ISNULL?

I've seen a lot of people use the COALESCE function in place of ISNULL. From internet searches, I've found that COALESCE is ANSI standard, so there is an advantage that we know what to expect when ...
9
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3answers
4k views

Oracle: How do I query a Hierarchical table?

Background This is for the construction of some views we'll be using for reporting. I have an table of locations, the key fields being "location" and "parent". The structure that these two fields ...
8
votes
1answer
198 views

Combine two event tables into a single timeline

Given two tables: CREATE TABLE foo (ts timestamp, foo text); CREATE TABLE bar (ts timestamp, bar text); I wish to write a query that returns values for ts, foo, and bar that represents a unified ...
8
votes
1answer
6k views

Insert with OUTPUT correlated to sub query table

I am modifying the structure of a database. The content of several columns of the table FinancialInstitution has to be transferred into the table Person. FinancialInstitution is linked to Person with ...
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votes
5answers
4k views

Query Running Differently on SQL 2005 vs SQL 2008R2

At my office, we have a query that is pretty ugly, but runs pretty well in production and in the development environment (20sec, and 4sec respectively). However in our testing environment it takes ...
7
votes
1answer
4k views

How do I get the aggregate of a window function in Postgres?

I have a table containing a two columns of permutations/combinations of integer arrays, and a third column containing a value, like so: CREATE TABLE foo ( perm integer[] NOT NULL, combo integer[] ...
6
votes
1answer
2k views

How to migrate between schemas in bulk in SQL Server?

We currently have multiple databases but would like to combine them and, instead, separate our domain contexts using schemas. In MS SQL Server 2008 R2, how can I relocate all the contents of one ...
6
votes
4answers
6k views

Passing in the table into a stored procedure

Is it possible to pass in the name of a table into a stored procedure? For example, suppose you have several views of the same table. They all have the exact same structure. You want a store ...
6
votes
1answer
2k views

Changing ANSI_NULLS setting on a table

Can we use the following query to update ANSI_NULLS option. sp_configure 'allow updates', 1 reconfigure with override update sysobjects set status = status | 0x20000000 where name = 'tblClient' ...
6
votes
3answers
16k views

Get Job id OR Job name from within executing job

I have a central DB that I write job outcomes on all my servers back to. I pass 3 parameters via powershell in a SQL job back to a sp on the central server that verifies the job should be running at ...
6
votes
2answers
952 views

Window functions cause awful execution plan when called from a view with external parametrized 'where' clause

I had this issue long time ago, I found a workaround which suited me and forgot about it. But now there's that question on SO so I'm willing to bring this problem up. There's a view that joins few ...
5
votes
3answers
8k views

Test if any fields are NULL

I'm trying to figure out an easy query I can do to test if a large table has a list of entries that has at least ONE blank (NULL / empty) value in ANY column. I need something like SELECT * FROM ...
5
votes
4answers
612 views

Group data by non-unique keys by distinct time range

I have data in my table like following... PROJ_NBR STATUS START_DT AL20 AC 1/14/2010 4:31 AL20 AC 1/14/2010 4:32 AL20 AC ...
4
votes
2answers
334 views

Postgres 9.4.4 query takes forever

We're running Postgres 9.4.4 on CentOS 6.5 and have a SELECT query that has worked for years, but stopped working and hangs after we upgraded from 9.2 (it took a while to notice it, so I don't know if ...
4
votes
2answers
7k views

How do I remove duplicate records in a join table in PostgreSQL?

I have a table that has a schema like this: create_table "questions_tags", :id => false, :force => true do |t| t.integer "question_id" t.integer "tag_id" end ...
4
votes
0answers
147 views

How to Audit for Access with Cross Database Ownership Chaining

I've just joined the data team of a new company and we have a large SQL Server environment (100+ instances) and cross database ownership chaining is on by what I gather is a necessity. I'm looking for ...
4
votes
1answer
932 views

Microsoft SQL Server 2008 - Catching user role changes with SQL Server Profiler?

I'm trying to figure out why one of my SQL server users keeps losing sysadmin role when I uninstall a particular program. Can I use the SQL Server Profiler to track down the action that causes this to ...
3
votes
3answers
392 views

Insert data between 30 minute time intervals

I want to divided my to my time interval depending to the start time and end time. To explain it further, let me have this example. I have this table: User Elapsed Time Start Time ...
3
votes
1answer
427 views

How will the order of operations in this query affect my results?

I've written a query, and I'm kinda sure that it does what it want. I'm thinking, "huh, I wonder if I know how Postgres works?". I'm going to list a specific assumption about this query below, and ...
3
votes
1answer
13k views

Restore Backup Fails - File 'Db' cannot be restored to '{…}.mdf'. Use WITH MOVE to identify a valid location for the file

I am getting the following errors trying to do a restore using the restore command on a backup file I recieved from a customer. RESTORE DATABASE SFDB FROM DISK = N'C:\Backup\Backup.bak' Any ...
3
votes
3answers
3k views

View foreign key constraints so I can delete a table

I have copied a database I was working on so I could change some key elements of its design for my new version. I want to delete totally some tables from the database however I cannot due to some ...
3
votes
2answers
14k views

SQL query that concatenate values from duplicate rows in a single table

Lets say I have a table of employees, like this: Name Sex Role Bob M Developer Joe M QA Now, I have a problem with this table of duplicated rows. I will fix it ...
2
votes
1answer
293 views

What's better here - a single column or multicolumn primary key?

Let's assume you have a table groups and a table item. Each item belongs to exactly one group. It is an inherent part of that group. An item cannot exist outside of a group and it cannot be moved to ...
2
votes
2answers
877 views

Optimize simple query using ORDER BY date and text

I have a query to a table in Postgres with an order based on a date field and a number field, this table has 1000000 records The data types of the table are: fcv_id = serial fcv_fecha_comprobante = ...
2
votes
2answers
4k views

MySQL case sensitivity for table names

Why is it that different platforms (linux vs windows) does not support the same naming conventions? I'm stunned by the fact that the documentation uses file names as an excuse for this. Yes, windows ...
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2answers
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How do I force a JOIN to use a specific index in MySQL?

I have a query that JOINs 2 tables; lineitem and part, select sum(l_extendedprice* (1 - l_discount)) as revenue from lineitem force index for join (l_pk), part where ( ...
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vote
1answer
6k views

Set permissions on all objects for SQL users

I have a procedure that loops through all objects in the database and assigns them proper permissions to that object. I want to know if there is a better way to do this? I use a model database to ...
0
votes
1answer
214 views

can i shrink log file in full recovery model

i have configured Always on Availability group where iam unable to shrink log file size through simple recovery model. can i shrink the log file size in full recovery model if yes or possible then is ...
0
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0answers
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Character set for 11.2 version database in oracle for sql* loader

NLS_NCHAR_CHARACTERSET AL16UTF16 NLS_LANGUAGE AMERICAN NLS_TERRITORY AMERICA NLS_CURRENCY $ NLS_ISO_CURRENCY AMERICA NLS_NUMERIC_CHARACTERS ...