Stack Overflow
Stack Overflow

Questions tagged [inner-join]

A database operation that combines the values of 2 tables based on a condition, or relationship, that exists between those tables.

An inner join is the most common join operation used in applications and can be regarded as the default join-type. Inner join creates a new result table by combining column values of two tables (A and B) based upon the join-predicate. The query compares each row of A with each row of B to find all pairs of rows which satisfy the join-predicate.

When the join-predicate is satisfied, column values for each matched pair of rows of A and B are combined into a result row. The result of the join can be defined as the outcome of first taking the Cartesian product (or Cross join) of all records in the tables (combining every record in table A with every record in table B) then returning all records which satisfy the join predicate.

Actual SQL implementations normally use other approaches like a hash join or a sort-merge join where possible, since computing the Cartesian product is very inefficient.

enter image description here

Resources :

6652 questions
14
votes
1 answer

Django eager loading in many to many

Those are many models class FacultyMember(models.Model): # some attributes class Publication(models.Model): # some attributes author = models.ManyToManyField(FacultyMember, blank=True) class Project(models.Model): # some…
Muhammed Hasan Celik
  • 672
  • 1
  • 8
  • 19
14
votes
1 answer

how to dplyr::inner_join multi tbls or data.frames in R

In R, how can I inner_join multiple tbls or data.frames effectively? For example: devtools::install_github("rstudio/EDAWR") library(EDAWR) library(dplyr) data(songs) data(artists) test <- songs colnames(test) <- c("song2", "name") inner_join(songs,…
Zhilong Jia
  • 2,329
  • 1
  • 22
  • 34
14
votes
4 answers

Left JOIN faster or Inner Join faster?

So... which one is faster (NULl value is not an issue), and are indexed. SELECT * FROM A JOIN B b ON b.id = a.id JOIN C c ON c.id = b.id WHERE A.id = '12345' Using Left Joins: SELECT * FROM A LEFT JOIN B ON B.id=A.bid LEFT JOIN C ON…
Murvinlai
  • 2,276
  • 6
  • 23
  • 34
14
votes
3 answers

how to prevent duplicates with inner join query (Postgres)

I am trying to understand how to create a query to filter out some results based on an inner join. Consider the following data: formulation_batch ----- id project_id name 1 1 F1.1 2 1 F1.2 3 1 F1.3 4 1 …
drkstr101
  • 760
  • 1
  • 6
  • 23
14
votes
2 answers

Convert nvarchar to int in order to join SQL tables in a view

I want to create a view which will display the info from two tables joined by different type fields. The one field is nvarchar and the other one is int. I know i need to convert one type in the other but don't know how to do it. Any help would be…
Charalampos Afionis
  • 193
  • 1
  • 1
  • 11
14
votes
3 answers

Ignore SQL INNER JOIN if there are no records to join?

I have the following Join INNER JOIN @SynonymTable AS A ON ([Products].[Title] LIKE A.[Synonym]) The @SynonymTable table variable contains (if needed) a list of items terms such as: %shirt% %blouse% %petticoat% These are all based on a list of a…
Nathan
  • 285
  • 1
  • 4
  • 10
14
votes
2 answers

Mysql Inner join with OR condition?

I have 2 tables like below location_distance ---------------------------------------------- id | fromLocid | toLocid | distance ---------------------------------------------- 1 | 3 | 5 | 70 2 | 6 | 8 …
jane
  • 161
  • 1
  • 2
  • 9
13
votes
1 answer

Ormlite inner join on three tables

i want to create an inner join on three tables like this one for example: SELECT C.Description, D.ItemDescription FROM OrderDetailStatement AS D INNER JOIN OrderHeaderStatement AS H ON H.OrderHeaderStatementRefID =…
Antonis
  • 1,061
  • 3
  • 18
  • 36
13
votes
1 answer

SQL where clause on inner joins

I am working with pgadminIII (postgreSQL) I have the following tables: Book, Publisher, OrderLine, ShopOrder. With the following SQL: SELECT Book.BookID AS "Book ID" ,Book.Title AS "Book title" ,SUM(OrderLine.quantity) AS "Number…
Edward Savage
  • 149
  • 1
  • 1
  • 9
13
votes
1 answer

Adding an INNER JOIN to a query should not increase the number of rows returned right?

I have a query like the following that returns the correct number of rows that I would expect. (It has to match a similar query that returns the same data sets but with different associated info from other related tables. SELECT * FROM LK INNER JOIN…
Kurt
  • 4,477
  • 2
  • 26
  • 34
13
votes
1 answer

Using index on inner join table in MySQL

I have table Foo with 200 million records and table Bar with 1000 records, they are connected many-to-one. There are indexes for columns Foo.someTime and Bar.someField. Also in Bar 900 records have someField of 1, 100 have someField of 2. (1) This…
Yurii Shylov
  • 1,219
  • 1
  • 10
  • 19
13
votes
3 answers

How to inner join tables from different Data Context?

I have two tables from two different Data Contexts. Although both tables are from the same database, two separate datacontexts exist. Error message: The query contains references to items defined on a different data context. How can I get…
jinsungy
  • 10,717
  • 24
  • 71
  • 79
12
votes
4 answers

Why is mySQL query, left join 'considerably' faster than my inner join

I've researched this, but I still cannot explain why: SELECT cl.`cl_boolean`, l.`l_name` FROM `card_legality` cl INNER JOIN `legality` l ON l.`legality_id` = cl.`legality_id` WHERE cl.`card_id` = 23155 Is significantly slower than: SELECT…
Ben
  • 251
  • 1
  • 5
  • 13
12
votes
1 answer

What's different between INTERSECT and JOIN?

Create data : CREATE TABLE sub1(id int,name nvarchar(7)); CREATE TABLE sub2(id int,name nvarchar(7)); INSERT INTO sub1 VALUES(1,'one1'); INSERT INTO sub2 VALUES(1,'one1'); INSERT INTO sub1 VALUES(2,'one2'); INSERT INTO sub2 VALUES(2,'one2'); INSERT…
Michael Phelps
  • 3,451
  • 7
  • 36
  • 64
12
votes
1 answer

Using inner Join in Solr query

In SQL, I have the query like this SELECT * FROM table1 INNER JOIN table2 ON table1.table1To2Id = table2.table2Id INNER JOIN table3 ON table1.table1To3Id = table3.table3Id How can I make the same query using Solr? Given that the field…
Tam Thai
  • 133
  • 1
  • 1
  • 6
1 2 3
…
99 100