An SQL join clause combines records from two or more tables or views.

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Updating a table efficiently using JOIN

I have a table that has the details of households and another that has the details of all the persons associated with the households. For the household table I have a primary key defined using two ...
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The order of INNER JOIN's

I would like to know if there are any rules about the order of INNER JOIN's in T-SQL 2000. I had 62x the performance on my query when my INNER JOIN that act like a filter is placed at first instead ...
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1answer
50 views

Getting related data from an uncertain column

I am working on a friendship logic, the table friendship has this structure: `friendship_id` INT NOT NULL , `user1_id` INT NOT NULL , `user2_id` INT NOT NULL , `status` INT NULL , `created` ...
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1answer
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SQL Server: Month Range Join [closed]

Given that there are two dates like 2012-07-08 and 2013-02-06. I need to count record of each user for every month. If there is no data for a user in particular month then it should return zero. The ...
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4answers
1k views

Table join to match without duplicates

I have a situation where I need to match arrivals and departures of assets in a location. The problem is that asset movements are not always entered into the database chronologically, nor is there ...
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2answers
78 views

Grouping results based on link table

I have three tables: users +----+-------+ | id | name | +----+-------+ | 1 | dave | | 2 | cher | | 3 | meg | | 4 | sarah | +----+-------+ groups +----+-------+ | id | name | ...
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2answers
619 views

Multiple JOIN of 6 tables via 5 database instances

I'm currently reengineering my corporates user management and created a table which lists all users of all the 5 database instances. Next step is, that I need to write a query which shows me all the ...
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1answer
736 views

Forcing Join Order

I have a table with just over a million rows. These rows can have a parent record in the same table which is found by joining to itself on 6 different columns (i.e. there is no single ParentID ...
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2answers
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How to use GROUP BY after the Having clause Mysql

Here is the query which gets the accounts for a specific user the products are related to accounts in one-to-many relation so for each product there are four permissions All the accounts which is not ...
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1answer
463 views

Simplify subqueries with join

I'm trying to create a report in SQL Server Reporting Services that shows the availability of multiple sites. The sites are monitored by a tool that uses a SQL Server 2012 database to store the data. ...
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1answer
45 views

Joining data from legacy database

I'm trying to figure out how to write this query. Table 1 - Booking BOOKING_ID | BOOKING_DATE | etc... 1 | 2013/01/01 | 2 | 2013/01/01 | Table 2 - BOOKING_PROCEDURE_TYPE ...
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2answers
234 views

Prune unused joins

I have expected that selecting from a view would not join the tables from which I don't query any values, but it doesn't seem to be the case. I have a bunch of tables with the following structure: ...
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3answers
68 views

find sold subscriptions from table 1 and store name in table 2, joined by store id. (oracle)

I am trying to get the number of sold subscriptions from one table and the store name from another. The tables have a common column containing a store id, however the columns do not have the same ...
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3answers
452 views

Will performance be better if I specify a filter multiple times?

Do I gain more performance if I repeat the filter in the WHERE clause on both sides of an OUTER JOIN? To clarify using code: select * from #main_select left outer join ( select main_id ...
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1answer
1k views

How to optimize multiple self-JOINs?

I'm looking for advice on either optimizing multiple self-joins, or a better table/DB design. One of the tables looks as follows (relevant cols only): CREATE TABLE IF NOT EXISTS CountryData ( ...
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1answer
4k views

Error “column does not exist” in a SELECT with JOIN and GROUP BY query

I'm using PostgreSQL 9.1 with a Ruby on Rails application. I'm trying to list the last version of each "charge" (in my history table : hist_version_charges) belonging to the same project id ...
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3answers
4k views

Splitting SQL query with many joins into smaller ones helps?

We need to do some reporting every night on our SQL Server 2008 R2. Calculating the reports takes several hours. In order to shorten the time we precalculate a table. This table is created based on ...
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1answer
924 views

HOW to “SUM” and “JOIN” for single query of a poll results?

I have a poll database as CREATE TABLE poll_answer answer_id, answer varchar(255), poll_id int(11), FOREIGN KEY(poll_id) REFERENCES polls(poll_id) ON DELETE CASCADE, PRIMARY KEY(answer_id) ) ...
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1answer
191 views

How to avoid large joins when determining which rows a user is authorized for?

Typical wep app situation: you have logged in users querying for resources exposed through an API. As a hypothetical example, company administrators quering for their employees' time sheets: company ...
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1answer
1k views

Best practice: Unions or a derived table?

I've inherited a medium-sized database with a terrible schema. The sanitized portion in question is like so: CREATE TABLE `pending` ( ... `invoice` int(11) DEFAULT NULL, `lid` int(11) DEFAULT ...
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1answer
420 views

Retrieving 10 records from multiple tables

I have two tables where I store post data. What I want to do is to get 10 records from those two tables. Table 1 - all posts, Table 2 posts that user read. There are some scenarios; User has never ...
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2answers
137 views

mysql join by 2 ways - how it works? - which gives performance difference

I had 2 different ways to query the content which showed performance difference when executed. The 1st way is EXPLAIN select SOME_COLUMNS from ( select * from A where CONDITION ) p inner join ( ...
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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? ...
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Join on different types

In a database I have two tables: The first has a field named taxonomy_id that is an integer The latter has a field named ID that is a character varying The two tables are related: if it exists a ...
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1answer
49 views

JOIN to read first table and get possible relationship in the second table

Consider a main table as CREATE TABLE groups ( group_id int(11) NOT NULL AUTO_INCREMENT, group_title varchar(255), PRIMARY KEY(group_id) ) ENGINE=InnoDB and a second table for relationship as ...
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1answer
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How can I include more query in one query?

These are my tables: tbl_answers => aid qid answer uid dateposted emailnotify namedisplay status isbestanswer tbl_questions => qid question ...
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2answers
280 views

Slow query joining on subqueries with max

I'm creating a report based on user input (i.e. a search tool) that grabs data from eight tables and will output them to the screen. Here are the create table statements. I'm very aware of how badly ...
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1answer
451 views

How to get rows where count() is null?

This is my SQL request : SELECT COUNT( b0_.id ) AS sclr0, d1_.codeLieu AS codeLieu1, d1_.nomLieu AS nomLieu2, d1_.lngLieu AS lngLieu3, d1_.latLieu AS latLieu4, m2_.libelleMention AS ...
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2answers
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Query WHERE clause and JOIN

I'm having an issue using a WHERE clause and JOIN. SELECT * FROM `CallDetailRecord` WHERE `StartTime` >=1357102799000 AND `StartTime` <=1357880399000 JOIN `CallEvent` ON `EventID` = ...
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3answers
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Column name naming conventions and best practices

I would like some expert opinion on best practices when it comes to column naming. The background is that according to Wikipedia, the following syntax, SELECT ... FROM Employees JOIN Timesheets ...
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241 views

Missing values in INNER JOIN MS-Access?

When I run the following query in MS-Access: SELECT a1.ConStateNumber, a2.ConStateNumber FROM qryW2_yr_sum_slash_qryW2_q4_sum_result a1 INNER JOIN qryW2_q3_sum a2 ON a1.ConStateNumber = ...
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3answers
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Left Join not giving desired result

I have two Datasets FEES PAYMENTS CrsCode InstNo FEE Regno CRSCODE Instno Payment CA1 -2 100 R1 CA1 -2 100 CA1 -1 200 ...
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1answer
612 views

How to add additional tables/fields into a query with multiple inner joins?

Given this query (many thanks to RolandoMySQLDBA from question Select records that do not have associations outside a certain list), how do I add other fields from other tables into my result? SELECT ...
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1answer
611 views

Get data from two tables with recursive relationships

I have a MySQL 5.1 DB, being used behind a PHP application to track permissions and other items that need to be issued to staff that hold various positions within an org. To track what privileges a ...
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1answer
1k views

Immediate refresh materialized views (MQT) with OUTER JOIN under DB2

DB2 accepts a materialized view based on an "OUTER JOIN" query, as long it doesn't refresh automatically (REFRESH IMMEDIATE). I cannot find a simple solution to get round this problem. Perhaps with ...
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1answer
49 views

Getting the name of the column that was used in a join?

This may be a bit of a weird question: Our project's datamodel has multiple tables with multiple columns any one of which can be used to join with one settingtable. The question here is how to get ...
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0answers
843 views

How can I join one to one to (many to one) without using group_concat

I have a table structure as follows: -- -- Table structure for table `emails` -- CREATE TABLE IF NOT EXISTS `emails` ( `ID` int(5) NOT NULL AUTO_INCREMENT, `email` varchar(255) COLLATE ...
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parenthetic grouping of join clauses

What is the difference between these joins? a left join b left join c (a left join b) left join c a left join (b left join c) Does the grouping only affect the order of the joins? Will the query ...
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2answers
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MySQL: Join one Row in a table with two Rows in other table

In my MYSQL Database COMPANY. I have two tables, like below in my diagram (arrow shows relations): `users` `user_login` +--------------+ ...
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1answer
338 views

Visually create a join using PHPMyAdmin

I recently started using SQL Server 2008 express and it has a really nice joins interface, whereby you can visually create a join. Is this possible on PHPMyAdmin?
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1answer
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Why is there such a huge performance difference in these two join statements?

I have a query which i first wrote as (query has been simplified a bit) : select ROW_NUMBER() OVER (ORDER BY c.CategoryTypeID), c.name, count(p.id) from category c inner join product p on p.indID = ...
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1answer
92 views

Speed efficient query for membership first joined, latest category from membership table (min, max)

I have the following table representing membership information: CREATE TABLE IF NOT EXISTS `membership` ( `id` int(11) NOT NULL AUTO_INCREMENT, `organisation_id` int(11) NOT NULL, ...
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1answer
7k views

Oracle: Non key-preserved table should be

I'm getting "ORA-01779: cannot modify a column which maps to a non key-preserved table" when I try to update a join. I've searched around the site and found a lot of advice on what key-preserved ...
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2answers
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Expand sparse table with self outer join on distinct values

I have this: g1 | g2 | x ---------+-----------+----- New York | Monday | 210 New York | Tuesday | 258 Chicago | Monday | 30 Chicago | Wednesday | 25 LA | Thursday | 40 ...
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2answers
1k views

Postgres RIGHT JOIN with custom array

I'm using Postgres 9.1 and want to get a result with some blanks where there is no data. My query looks like the following: SELECT institution_id FROM ... WHERE institution_id IN (1, 3, 4, 5, 7, 9) ...
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1answer
281 views

How to write this self join based on three columns

Hello there I have a following table ------------------------------------------ | id | language | parentid | no_daughter | ------------------------------------------ | 1 | 1 | 0 | ...
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1answer
338 views

join the two tables which possess one to many relationship

In drupal,the content type table and my own table is used to do some operations. Im having two tables namely Table1:'content_field_mem_id' & Table2:'Ex' description of ...
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1answer
573 views

oracle huge hash_area_size

I am wondering what is the maximum setting for hash_area_size parameter? I'm trying to perform a huge join which ends up allocating 10Gb of temp space and completes in an hour. 10Gb is not that much ...
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1answer
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Selecting minimum value using a subquery

I need to write a query to grab the lowest price from each merchant and output the price link (p_link) and some other information such as merchant name + rating. We have a table for prices ...
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1answer
137 views

Join Calender Table

I have a Datatable and a Calendartable. I do a join on this tables to get sequential dates if there is no data for this day. My problem now is that there a several id's and i need a count for each ...