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

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What's the point of SQL joins if you have OLAP?

I want to understand the purpose of using SQL joins from a business analysis perspective. Let's say I want to analyze customer data. Why would I want to pull data from multiple tables using join ...
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31 views

Use join to aggregate data from various normalized tables

I have a database as follows: tbl_clients (Primary Key: client_id, Foreign Keys:place_id,district_id,zone_id,country_id) tbl_places (Primary Key: place_id) tbl_districts (Primary key: district_id) ...
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232 views

How to optimize a very slow query with joins and group by?

I have this GTFS database : All the ***_id columns are indexed, and there are foreign keys between tables (such as a FK on trips.route_id to routes.route_id). So basically the link between a stop ...
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31 views

Mysql join not working

I have database with two tables: logs & src_info mysql> describe logs; +-----------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | ...
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29 views

Calculations involving thresholds between two tables

I have a table comment and a table price like below. The key columns in both tables are ticker_id, price_datetime and price_open. The last column threshold in table comment (which currently NULL) is ...
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31 views

Footer with counter of records, using union of query

I have a report that has a header (display the current date), I use UNION to join the header with the main query that returns multiple records, it has 10 columns. After that another UNION for joining ...
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USING construct in JOIN clause can introduce optimization barriers in certain cases?

It was brought to my attention that the USING construct (instead of ON) in the FROM clause of SELECT queries might introduce optimization barriers in certain cases. I mean this key word: SELECT * ...
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36 views

Can I optimize a left join for a single match?

Consider a join A LEFT JOIN B ON A.id = B.a_id: B.a_id is nullable -- most but not all B records point to an A record. A can, at most, only have one matching B record (business logic). Not all A ...
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42 views

Joining WordPress Comments with Post Titles from MySQL DB

I'm working with a wordpress database and need to get some data on the comments. The goal is to get comments from a decommissioned site. I have the database running on my local system and can ...
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51 views

Is it possible to pick next row's cell value on same column if condition not matched?

I have a table flaggedcomment and a table price. In flaggedcomment, there are two empty columns Price_DateTime and Price_Open which I want to copy from price, depending on the ON conditions. Query as ...
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2answers
49 views

join value in a RETURNING which is not inserted

Im doing an insert from a query which joins two tables, then I want the new ID from the inserted row, and a field from the original row which is not involved in the insert.Is it possible? I get a ...
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572 views

Getting around the constraint “column must appear in the GROUP BY clause or be used in an aggregate function”

I'm using Postgres, which enforces the constraint that all columns in a SELECT...GROUP BY must appear in the GROUP BY clause or be used in an aggregate function. Lets say I'm modelling peoples' cars, ...
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39 views

Inner join and group by [closed]

So I've got two tables. Accounts has three columns: id, Account_ID, Account_Name Tickets also has three columns: id, Account_ID, Description I can use the following query to get the most ...
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45 views

MySQL Query Causing Massive Slowdown Over Time

I've been experiencing massive slowdown on my server after launching a new website. Using MONyog I can see that after an apache/mysql restart, the queries/second starts out nice and low for around 10 ...
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1answer
58 views

Join conditions and Where conditions in Left Join

STUDENT table contains a list of students in my school Database LIBRARY_BOOK table contains the information of each Book that is with currently with any student. each student is allowed only 1 book ...
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100 views

What indexes should one use to optimize a PostgreSQL query with a JOIN depth of 2?

Disclaimer: I am relatively new to PostgreSQL. I'm wondering how to optimize a query that does 2 INNER JOINs. My scenario is fairly simple: Select Posts with a photo (Posts.photo IS NOT NULL) and a ...
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48 views

same table on different commands (inner join)

Testing some commands of MySQL, I've come across these two comands resulting on the same table. Command 1: select sales.relatory_code, sales.date, destiny.exportation_name from sales, destiny where ...
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Local Server Slow When Joining

I have two cira 600MB tables that I am querying as such: SELECT id, name, url FROM names, urls WHERE metaphone = 'ALX;FLX' AND urlId = urlRef; This runs fine on my live server ( ~ 0.02 sec,) but on ...
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130 views

select values from a table where column values should be different [closed]

Let us say there are 4 columns in a table . cpt,cpt4mod,itemcharge,eff_date. condition1: if the values of cpt,cpt4 and itemcharge are same, but eff_date is different. Then I need to fetch the ...
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127 views

Understanding multiple table join with aggregation

I have a basic question on how JOIN works on multiple tables. I want to count occurrences of Foreign Key in link1 & link2 CREATE TABLE main ( id SERIAL PRIMARY KEY, name text NOT NULL ); ...
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1answer
56 views

Compare two columns for difference mark the difference in mysql

I need to compare two fields and mark the similar fields in third table. For Example: Tables customer: phone id, phonenumber followstatus received_Customer: rc_id, rc_phonenumber. I ...
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1answer
193 views

Sorting Table and get Position of row

I have a Table with 3 rows. Player, Time, Server. Now, I want 2 things and I don't know how. For Server there are 3 worths available. 1, 2 and 3. Server and Player are a Primary Key together. User ...
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Outer Apply vs Left Join Performance

I am Using SQL SERVER 2008 R2 I just came across APPLY in SQL and loved how it solves query problems for so many cases, Many of the tables I was using 2 left join to get the result, I was able to ...
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How to join fixed row table against mapping table and reveal unmapped records

I have two tables and I am having trouble figuring out how to join them to meet my projection needs. Here is a scenario that illustrates the problem 1. The first table has a fixed set of values/rows; ...
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132 views

SELECT query with DISTINCT on a table-structure for graphs is very slow

I have 2 tables where nodes contains about 60m rows and edges about 500m rows (both growing fast). These two tables represent a directed graph. CREATE TABLE edges ( node_from bigint NOT NULL, ...
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Get all (non repeated) distribuidores with their paises given a producto_solicitud

I have this schema: And as title says I need to get all records from fabricante_distribuidor by given producto_solicitud.id value. I'm doing in this way: SELECT ...
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86 views

Sort by number of related rows in referencing table

Let there be two tables: Users id [pk] | name --------+--------- 1 | Alice 2 | Bob 3 | Charlie 4 | Dan Emails id | user_id | email ----+---------+------- 1 | 1 ...
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58 views

How to join a table with a table valued function?

I have a user defined function: create function ut_FooFunc(@fooID bigint, @anotherParam tinyint) returns @tbl Table (Field1 int, Field2 varchar(100)) as begin -- blah blah end Now I want to join ...
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59 views

SQL query to aggregate data from three tables

I have the following three tables: The "users" table: user_id first_name last_name username password The "users_addresses" table: address_id user_id street country_id email The "countries" ...
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29 views

MySQL join for two queries

I have the following two queries... mysql> select id, title from events; +----+-----------------------------------------------------------------------------------------------+ | id | title ...
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2k views

Sql server table insert performance optimization

Setting In a datawarehouse, I am joining a fact table to 20 dimensions. The fact table has 32 million rows and 30 columns. This is a temporary staging table so I don't have to deal with other users ...
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MySQL Multi Count and Filter

Table: Event ============== ID OldUserID NewUserID Date Table: User ============== ID Forename Lastname .... How can i filter by date column like so... this code is pseudo... SELECT ...
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How to create the multiple sum query with joins

Please consider following database: Table `invoices`: -- invoice_id Table `amounts`: -- amount_id invoice_id type_id amount I am trying to get the sum for each type from table like this: SELECT ...
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optimize my query mysql

I have the following query: SELECT DISTINCT d.movieName, d.castName, d.movieImdbId, f.year, f.posterLink FROM director_movie as d LEFT JOIN film_info as f ON d.movieImdbId = f.ImdbId WHERE d.castName ...
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Simple left outer join leaving me with inner join

So I have a table with each record being a change to an object. e.g. in the app you open your project with a project id in this project you edit an object name hit save that generates new record ...
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Is it better to separate a big query into multiple smaller queries?

There are situations which require having really big query joining several tables together with sub select statements in them to produce the desired results. My question is, should we consider ...
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468 views

Build a three table join with a recusive table in the middle?

I have three relevant tables: Parts, PartGroup, and MarkupGroup. Parts is simple. PartID artificial primary key Part part number PartGroupID Foreign key sample data: 1 ...
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1answer
73 views

Massive joins Vs Updating temp table

I'm working on a query that essentially aggregates a slew of tables together. The first method I tried was to inner join all of the tables into one nice big query that pretty much looked like this: ...
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63 views

Summarizing Pay Checks Based on Employee's Job Code

What I'm trying to do is summarize an employee's earnings for each job code they worked in for the year. Employees are assigned a job code based on an effective date. I'm trying to line up the job ...
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Joining two Mysql VIEWs takes a very long time

I have a textbox (for which I used jQuery auto-completion) in my PHP form where user can insert an actor/actress name and then by clicking "Search" button, a new window is opened showing list of ...
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How can I simplify this UNION?

Here's the case - I have the following query: SELECT DISTINCT post_id FROM ( ( SELECT DISTINCT rp.post_id, pm.meta_value AS premiere_date FROM wp_related_people AS rp JOIN ...
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61 views

Companies and addresses MySQL [closed]

I've got a database with 2 tables. companies addresses These are my tables. Adresses adress_id adress_adress adress_adressnumber adress_zipcode adress_city adress_postbus adress_country ...
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111 views

Join select queries on an id in SQL Server

I have three tables that SELECT from and I'd need to join the results. It feels like this should be a rather easy task but I struggle with the syntax. Working on Microsoft SQL Server Enterprise ...
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1answer
111 views

Select two aggregate functions on the same column using different criteria - performance

Dear stack exchange users, first question here. The database in question is a service database where a user hires a service. Now I would like to show the person that was hired an overview of how many ...
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1answer
69 views

How to manipulate join order of PostgreSQL optimizer?

I am working on table join order optimization. While query processing, I want to get table join order generated by optimizer, and update it by using my own algorithm in PostgreSQL? How can I update ...
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1answer
70 views

mysql join not working as expected

i want to select schedule of specific teacher for a given day .... statement should assume that a teacher may teach in elementary and high school here is my statement `select class.name as ...
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380 views

Query optimization for multiple joins postgres

ER Diagram Brief description The database to be used is postgres. The database might contain upto 2 million AccountHolder records. Since the AccountHolder table is accessed and updated frequently ...
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53 views

Updating MySQL innodb table based on multiple joins

I have a table with the following (slightly simplified) structure CREATE TABLE `oak_relation` ( `o_id` int(10) unsigned NOT NULL, `k_id` bigint(20) unsigned NOT NULL, `initial` float unsigned NOT ...
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MySQL improve query syntax

I have this simple MySQL query: SELECT * FROM table1 INNER JOIN table2 ON table2.col = table1.id WHERE table1.id = '123' id is the primary key in table1. table2 has composite primary key of two ...
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Join does not not use index in PostgreSQL?

I have a statement that selects from two tables news and status. It seems that the index on the column status of the table news is not used. This table has about 70.000 rows and the query costs too ...