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

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Deadlock when update different rows with non-clustered index

I'm solving a deadlocking issue while I noticed the lock behavior is different when I use clustered and non-clustered index on the id field. The deadlock issue seems to be solved if clusted index or ...
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2answers
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Efficient query to get greatest value per group from big table

Given the table: Column | Type id | integer latitude | numeric(9,6) longitude | numeric(9,6) ...
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3answers
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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 ...
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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 ...
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2answers
263 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 , ...
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1answer
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Why does a query run slower in a Stored Procedure than in the Query window?

I have a complex query which runs in 2 seconds in the query window, but about 5 minutes as a Stored Procedure. Why is it taking so much longer to run as a stored procedure? Here's what my query looks ...
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1answer
185 views

Why is query thousands of times slower with DESC?

I have a PostgreSQL database (AWS RDS) and ran the following queries in psql: livenet=> EXPLAIN ANALYZE SELECT * FROM outputs ORDER BY height LIMIT 10; Limit (cost=0.57..36.82 rows=10 ...
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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 ...
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4answers
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Is a join optimized to a where clause at runtime?

When I write a query like this... select * from table1 t1 join table2 t2 on t1.id = t2.id Does the SQL optimizer, not sure if that is the correct term, translate that to... select * from table1 ...
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Do you know an easy way to generate one record for each hour of the past 12 hours?

I have a report that shows the count of events for the past 12 hours, grouped by the hour. Sounds easy enough, but what I am struggling with is how to include records that cover the gaps. Here is an ...
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3answers
562 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 ...
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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 ...
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How to list all views in SQL in PostgreSQL?

How do I list all views for a database using an SQL command in PostgreSQL? I would like something similar to output of the psql \dv command, but preferably just a list of view names. e.g., SELECT ...
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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 ...
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3answers
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Used Memory not freed up after a SQL BULK Insert / BCP Export

I have created a very basic SQL table as following CREATE TABLE [dbo].[TickData]( [Date] [varchar](12) NULL, [Time] [varchar](12) NOT NULL, [Symbol] [varchar](12) NOT NULL, [Side] [varchar](2) ...
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Best practice between using LEFT JOIN or NOT EXISTS

Is there a best practice between using a LEFT JOIN or a NOT EXISTS format? What is benefit to using one over the other? If none, which should be preferred? SELECT * FROM tableA A LEFT JOIN tableB B ...
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Storing date as integer (numeric), what are the advantages

Question 1 I am working with a system where date is stored as integer (actual numeric(8,0)) and I have noticed that other systems also store date as int such as cisco in this thread. Example ...
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overstating field size in database design

I have some fields for my tables that are strings and at the moment, most of the field size have pretty high character limits. For instance, 100 char for the street name. Is there a penalty for using ...
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How to avoid a cyclic dependency (circular reference) between 3 tables?

I have 3 tables: People Post Likes When I design the ER model it has a cyclic dependency: 1:N People --------< Post 1:N Post ----------< Likes 1:N People ...
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How to check if a subquery has exactly one distinct result and a specified value concisely?

I found myself writing the following: select 'yes' where exists(select * from foo where val=1) and not exists(select * from foo where val<>1); and wondering if there is a more concise way ...
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4answers
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SQL Server 2005/8 Query Optimisation Hints

I'm looking at educating a team on writing better SQL Server queries and was wondering what people's best hints were for improving performance. For instance I once had a DBA who insisted that ...
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1answer
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Could a null column be part of a primary key?

I'm developing a SQL Server 2012 database and I have a question about a One-to-Zero-Or-One relationship. I have two tables, Codes and HelperCodes. A code could have zero or one helper code. This is ...
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What does NVL stand for?

What does NVL stand for? I'm talking about the Oracle and Informix (perhaps some others too) function used to filter out non NULL values from query results (similar to COALESCE in other databases).
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How to Log All mysql queries into log file?

I am using Mysql 5.6.12 under Wamp server environment. Now I want to log All queries into ".log" file, the queries which are running by PHP or from PHPMyAdmin, I want to log them...
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What is the best way to find out how many records do not have a proper phone number in SQL Server?

I have a field that people historically could use to freely supply a value. I need to identify the records which do not have an appropriate value so I can clean them. I've been looking around in SSIS ...
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Is there a way to programmatically script all objects associated with a given table?

I know that in SQL management studio I can right click a table/trigger/key and script object as.... Is there a way to do this programmatically, given an object's name? If so, is there a way to find ...
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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 ...
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How can I optimize this MySQL query further?

I have a query that is taking a particularly long time to run (15+ seconds) and it is only getting worse with time as my dataset grows. I have optimized this in the past, and have added indices, ...
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Why does MySQL allow HAVING to use SELECT aliases?

In SQL, as far as I know, the logical query processing order, which is the conceptual interpretation order, starts with FROM in the following way: FROM WHERE GROUP BY HAVING SELECT ORDER BY ...
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2answers
720 views

function hangs with null case operation

I created a function that accepts a start and end date, with the end date being optional. I then wrote a CASE in the filter to use the start date if no end date is passed. CASE WHEN @dateEnd IS NULL ...
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6answers
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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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How to delete a procedure which name is ambigous?

I am using informix... I dont know how i did it, but there are two procedures with the same name in my database. When i try to remove them with a DROP PROCEDURE myProc; then i get a error message ...
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SELECT DISTINCT on one column, while returning the other columns?

I have a query which uses three lookup tables to get all the information I need. I need to have DISTINCT values for one column, however I also need the rest of the data associated with it. My SQL ...
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2answers
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How to wrap long lines when SELECTing SQL text columns?

I'm selecting from a table with long text columns. I'd like to wrap long lines to a maximum line length. From: SELECT * FROM test; test_id | text ...
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2answers
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LNNVL Justification

LNNVL is an oracle built in function that returns TRUE for conditions evaluating to FALSE or UNKNOWN, and returns FALSE for conditions evaluating to TRUE. My question is what would be the benefit of ...
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1answer
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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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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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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 ...
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2answers
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foreign key constraint violation issue

I have identified 3 situations. A student with no enrollments. A student with enrollments but no grades. A student with enrollments and grades. There is a trigger on the enrollments table to ...
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3answers
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SQL Server 2008 datetime index performance bug

We are using SQL Server 2008 R2, and have a very large (100M+ rows) table with a primary id index, and a datetime column with a nonclustered index. We are seeing some highly unusual client/server ...
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2answers
6k views

Updating 700 million rows to same value

I've got a data warehouse (oracle) where I need to set a column to the same value for all 700 million rows. I don't have admin access, or access to an admin, so this needs to be accomplished with ...
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2answers
253 views

Find rows where integer sequence contains a given subsequence

Problem Note: I refer to the mathematical sequences, not the sequences mechanism of PostgreSQL. I have a table representing sequences of integers. The definition are: CREATE TABLE sequences ( id ...
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2answers
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How does using separate schemas affect SQL Server 2008 performance?

I want to use separate schemas for objects with different purposes in our SQL Server 2008 database. Right now we use a fairly mind-numbing naming convention to indicate the purpose of a table or ...
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2answers
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Slow Performance Inserting Few Rows Into Huge Table

We have a process that takes data from stores and updates a company-wide inventory table. This table has rows for every store by date and by item. At customers with many stores, this table can get ...
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3answers
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Treating certain Arabic characters as identical

In Arabic we have characters like ا (alef) and أ (alef with hamza). Users write them interchangeably and we want to search them interchangeably. SQL Server treats them as separate characters. How ...
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5answers
818 views

Efficiently Filter Large Set With Disjunctions

Let's say I have a single table CREATE TABLE Ticket ( TicketId int NOT NULL, InsertDateTime datetime NOT NULL, SiteId int NOT NULL, StatusId tinyint NOT NULL, AssignedId int NULL, ...
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245 views

Bulk insert M:N relation in PostgreSQL

I need to import data from an old database to a new one, with slightly different structure. For example, in the old database, there is a table recording employees and their supervisors: CREATE TABLE ...
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4answers
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Execute a script with SQLPlus containing blanks, semi-colons, and forward slashes

Occasionally I will get a script that will run fine in SQL Developer or Toad, but requires modification in order to be run successfully from SQL*Plus. Here is a worst case example containing multiple ...
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Fast SQL query with * but extremely slow with specific columns? [closed]

We have a query that we're running on SQL Server 2008 in the Management Studio. I can't give the exact query details, but let's say it's equivalent to this: SELECT * FROM MyView a (nolock) INNER ...
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5answers
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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 ...