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

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Update a field in table when a combination of three fields with a second table is matched

I have a database form an old archaeological project which I imported into a mysql DB. I have a table "graves" with 400+ entries: "graves" id necr burials single multi 1 1 1 ...
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Select MAX DATE from joined Table

I have two tables, PROJECT and BILLINGS, as follows: Project_ID Project_Client ---------- ------------------ P1 ABC Company P2 DEF Company P3 GHI Company Proj_ID ...
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Optimizing a query that performs worse on a smaller dataset

I am trying to run this query. The * is just for simplification, I'm selecting ~10 specific fields for some calculations. SELECT * FROM `orders` LEFT JOIN `orders_processed` ON ...
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Matching single column against multiple values without self-joining table in MySQL

We have a table that we use to store answers to questions. We need to be able to find users that have certain answers to particular questions. So, if our table consists of the following data: user_id ...
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1answer
231 views

Data Analysis with MongoDB or MySQL

I have a need for processing some data in order to come up with some statistic. This is the scenario: Each user can answer several questions from the question list. They pick their answers from a ...
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Estimate the number of Tuples from relations

Quick question, and great help if possible: I have an exam tomorrow on a database module which I'm revising for, and one of the past papers had this question: Consider the following three relations: ...
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1answer
189 views

SQL SELECT - adding field to SELECT with JOIN is changing the results

I have a SQL sentence with JOIN, running on mysql 5.5.16: SELECT DISTINCT (ot.orders_id), ot.value FROM orders_status_history osh INNER JOIN orders_total ot ON ( osh.orders_id = ot.orders_id ) WHERE ...
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24 views

How to remove data from multiple tables with different foreign keys without using ON DELETE CASCADE?

I have the following SELECT statement: SELECT * FROM "Users" u INNER JOIN "Calendars" c ON (u."UserId" = c."UserId") INNER JOIN "Actions" a ON (c."CalendarId" = a."Calendar_CalendarId") WHERE ...
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130 views

Minimizing Page Fetches

I have a complicated database structure and am trying to use it to retrieve Records based on multiple selection criteria from several tables. As a general rule, is it better to attempt to use ...
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1answer
346 views

Does MySQL load the entire row into memory, or just the columns used in WHERE, ORDER BY and GROUP BY?

I have a table that isn't very large row wise (in the 100ks range), but that contains a lot of raw data that is very large in size. Despite having a relatively little number of rows, it's around ...
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355 views

Mysql improve Self join performance large table?

I have a task to help identify conflicting IP ranges , I want to highlight when one companies IP range falls within another's ... below is the sample table, I have converted the IP ranges from .dot ...
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1answer
40 views

MySQL select with join table

I have 3 tables, one of them is join table: user table: CREATE TABLE `user` ( `id`, `name`) media table: CREATE TABLE `media` ( `id`, `value`, `type` enum('M', 'T')) user_media table: CREATE ...
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Select range of non-identical date from different table

On MySQL5 with innoDB, I have sensor data in multiple tables, all with an ID and a DATETIME field, like so (two tables shown, but there are more). The IDs and DATETIMEs are not identical between ...
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1answer
19 views

How do I merge two rows only if there is the TagWidgetIds are same but the tagValues are different?

I have this stored procedure which generates the following output. The query which generates the output from the stored procedure is as follows: SELECT tat.[agent-id], ...
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1answer
32 views

What is the most efficient way to exclude records with a particular ID in a MySQL query for random records?

I have an api endpoint that returns X amount of random posts from a table called "posts". This endpoint is used by a mobile app. It retreives random posts by doing a SELECT COUNT(*) on the posts table ...
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2answers
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How to Create key (to be used in join) using concatenation?

I want to inner join tables in SQL Server 2008, however both tables have been set without Primary Keys. How to create a key using concatenation of existing columns? I tried the below but it only ...
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2answers
29 views

Table JOIN and CREATE new table extremely slow

I'm using something like this to create a new table: CREATE TABLE result AS (SELECT calls.*, targ_with_planned_calls.* FROM calls INNER JOIN planned ON calls.first_id = ...
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1answer
168 views

Joining on a field with different values

I am trying to join data from two completely different sources. One source contains an employee's schedule information, and the other tracks what they actually worked (like what time they actually ...
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99 views

MySQL JOIN query produces wrong result

I have two tables complaints and complaints_reply in my MySQl database. Users can add complaints which are stored in complaints the complaints reply are stored in complaints_reply table. I am trying ...
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25 views

How to display all the dates between multiple two dates in a table?

I want to display all the dates between two dates for a particular record And this is the table : ID Start_Date End_Date 1 2013-01-14 2013-01-18 2 2013-02-01 2013-02-04 and now i want to get all ...
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2answers
198 views

MYSQL joining 3 tables with left join

I have these tables: pupils: (id_pupil, name, surname, email, user, pass, level, class) incidents: (id_incidents, date, time, type_incident, comments, id_pupil, id_user, subject, id_trimester) ...
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2answers
129 views

Calculating percentage from two tables

I have two tables: First one contains unique mentees under one mentor, so mentors can have more than one mentee in that table. Second one contains interactions of mentors with mentees on different ...
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127 views

How to optimize a query so that it seeks on one index first, and then another index after that

I have two sets of earth measurements from satellite data, each with time fields (mjd for mean julian date) and geography positions (GeoPoint, spacial) and I'm looking for coincidences between the two ...
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1answer
3k views

UPDATE a column by COUNT of another table

It might be a naive question, but what is the difference of these two queries and which is preferred? UPDATE table1, (SELECT id,COUNT(*) idcount FROM table2 GROUP BY id) AS B SET table1.Freq = ...
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Join more than 3 tables in one single query, with many comparisons and no IDs

I use an overlycomplex and poorly designed software at my work, and now I need to produce a report of invoices issued between a period of time. Invoices are held at table ENTR2012, which uses the ...
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341 views

How to improve the performance of SELECT queries with multiple JOINs on a 50GB database hosted on AWS m3.medium MySQL RDS?

Example query: SELECT p.ListAgentEmail, p.ListAgentFirstName, p.ListAgentLastName, p.ListingKey FROM Property_RES AS p INNER JOIN Property_RES_COUNTIES_OR_REGIONS ON ...
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40 views

INTERSECT query rewrite as JOIN?

I have two queries written in PHP against a Microsoft SQL Server database (I know this is weird). I'm querying one table. I want the records shared by both results sets ONLY. Here is query #1: ...
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1answer
352 views

MySQL update one table from another joined many-to-many

I have two tables, events and plays joined many-to-many by a third table plays_in_events. Where the events.Name field is blank, I want to set it equal to the name of the play that was performed in ...
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85 views

Query with group by having count 0

I am working on application for managing football league as my homework. I want filter list of players by number of matches they have played in league. For example user can enter count > 0 and count ...
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1answer
168 views

How can I optimize this Cross Table COUNT() mysql query?

I am trying to cut down the retrieval speed of this MySQL query. All instances of COUNT() point to the PRIMARY key of each field. Currently this query makes my MySQL hang. It seems ridiculous as I'm ...
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1k views

How to find the nth highest salary in SQL?

I have found a query to find the nth highest salary from Employee table , but i don't understand the logic of (N-1)? EmpID Salary 1 90000 2 80000 3 54000 4 ...
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25 views

How to improve performance when joining against coalesce

In an effort to remove a caching layer from our application, I'm building a number of views to encapsulate the different ways a user can have access to a piece of content - one per "rule" of access. ...
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69 views

Selecting most recent date when dates are stored in another table

Working in a MySQL database, I have tables set up like this: Table song_instances has song_id (int), meeting_instance_id (int) The meeting_instances table has columns meeting_instance_id (int), ...
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Retrieve multiple rows from table2 based on single row from table1 in SQL Server [duplicate]

I have two tables and I am using SQL Server. table1 structure is Campiagn_Id Campiagn_Name 1 test1 2 test2 3 test3 and table2 structure is Campign_Id EmalList ...
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1answer
26 views

How to join tables without identifiers?

For school I have to do this: Query what salary scale an employee belongs to displaying these collumns: s_schaal.schaal, werknemer.name, werknemer.salaris. But there are no identifiers between the ...
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3answers
226 views

SQL join with multiple columns as FK to same list table

I have a table that has 5 references to a list table for normalization of the first table. So in the table 1 a row looks line other columns..., reference_1, reference_2, reference_3, reference_4, ...
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Join two tables and return data and count in a single query

I have two tables in an SQL Server database, one with two columns and one with four: tbl_email_list email_list_id int (PK) email_list_name varchar tbl_email-details email_uniq_id int (PK) ...
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1answer
49 views

Inner join on array column in Postgres

In Postgres 9.4, I'm trying to pull the names of all columns that are involved in a UNIQUE constraint for a given table in Postgres. It looks like the names of such columns are contained in ...
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50 views

inner join select - group by?

I have 2 tables (Oracle database): ANEXA2A_TABEL1: id fk_id_anexa pet1 pet2 alt1 alt2 1 123 10 1 20 2 2 321 11 2 10 3 ...
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making a where clause optional in a sql statement

Here is my current query: `SELECT `performers`.`hash`, `performers`.`alias`, `performers`.`date_updated`, `performers`.`status`, IF(`performers`.`status` = 'active', 'deleted','active') AS ...
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Interpretation of multiple join order

I have a problem using multiple joins in one SQL Statement. For example, I have 10 Tables which are tbl1, tbl2, tbl3,..,tbl10. I would like to select some columns from each table. If I use joins in ...
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577 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) ...
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How to calculate sum of a column in a table accessed with multiple joins and where condition

I am unable to find correct sum of vaccinated based on campaign id. no matter which campaign I choose to get sum of vaccinated on the basis of that campaign id it always returns the same data. Please ...
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1answer
50 views

Oracle 11g hash join vs nested loops question

I'm using Oracle 11g and working on a legacy system. I have two tables, A and B. A has ~40M rows and B ~4M rows. A has a foreign key on B (B is the parent of A). A query does essentially this: ...
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How to display additional column in select with true/false value [SOLVED]

Solved. Look in comment. I am using PostgreSQL 9.1. I have 3 tables: simcards: id serial NOT NULL, iccid character varying(30) NOT NULL, customer_id integer customer: id serial NOT NULL, name ...
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Meaning of JOINs in sql

I was trying to interpret the relationship between JOINs like LEFT-OUTER JOIN, RIGHT-OUTER JOIN, etc with relationships like Many-To-Many, One-To-Many etc in Hibernate or database language.
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how to fetch different data on compare rows of two tables

I have two tables in my database, one is user_app table in which user info are stored, table are as: +--------------+--------------+------+-----+-------------------+-----------------------------+ | ...
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1answer
77 views

Is it possible to simplify a query with multiple joins to the same table?

I have a rather large query which takes longer to run than I would like because of 17 LEFT JOINs on the same table. I've done some searching, but haven't found anything that is really similar to my ...
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1answer
221 views

Left outer join not returning all rows in a grouping query

I'm trying to query all users to find the price of orders in the last month. I'm doing this on PostgreSQL. Here's a toy database to show my problem: I have a people table and an orders table. I'm ...
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Is there a way I can speed up queries against this particular view?

I have three tables in a PostgreSQL database that I'm querying via a view and some joins. CREATE TABLE network_info ( network CIDR NOT NULL, some_info TEXT NULL, ...