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

learn more… | top users | synonyms

0
votes
1answer
47 views

Problem JOINing three tables

I want to show all the categories and the items inside that each category which should store in items_this_category. Note, I have created an associative table item_categories because one item can be ...
0
votes
1answer
31 views

whether to merge partitioned table with only partially overlapping columns

I opted for MonetDB for my static data, but this might be less of a MonetDB-specific question about features than about RDBMS (or just SQL) in general. I have data with a few "cross-sectional" ...
1
vote
1answer
94 views

Performance issues when extracting scatter plot data

First off: Sorry for the title, couldn't think of anything better. Feel free to change it though. Ok, assume I have the following table: ...
1
vote
1answer
62 views

Joining three tables

I have a question Find the titles of all movies not reviewed by Chris Jackson Where the relations are 3 movie(mID, title, year, director), reviewer(rID, name), rating(rID, mID, stars, ratingDate) ...
6
votes
3answers
9k views

How to SELECT multiple COUNT(*) columns with each GROUP BY having a different WHERE clause?

I have the following schema: CREATE TABLE Person ( PersonId int PRIMARY KEY ) CREATE TABLE Action ( ActionId int PRIMARY KEY, PersonId int NOT NULL FOREIGN KEY REFERENCES Person(PersonId), ...
0
votes
0answers
65 views

Very slow inner join

newby on mysql so help needed I created a my sql query, on their own they run fast but when I enter the inner join it runs forever. i did index theres id tables but no result in speed. here is my ...
1
vote
1answer
56 views

How can I make multiple joins on the same table?

I have a table (signal) which contains references to two other tables (ee and eeav). I want to perform an SQL Query which combines the data from ee and eeav tables. The situation is as follows: The ...
0
votes
1answer
48 views

Linking Two database to execute join query

I have a remote odbc connexion and an MySQL database in my localhost i ask if there is a way to execute a join query ( linking the two database ) ? thanks.
0
votes
0answers
194 views

MySQL: Is it possible to join a virtual table with itself?

I am not sure if 'virtual table' is the correct phrase. I am instantiating a table X like so: SELECT * FROM ([some select subquery]) X and I would like to cross join that table with itself several ...
1
vote
1answer
302 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 ...
4
votes
1answer
333 views

MySQL - GROUP_CONCAT returns duplicate data, can't use DISTINCT

I have a normalized database and I'm trying to return data from multiple tables using JOINs and GROUP_CONCAT. Problem: Rows are being duplicated with GROUP_CONCAT. I can't use DISTINCT because some ...
1
vote
2answers
577 views

How to delete rows from a table when we're joining and return data?

I have two queries: The first one is as below: SELECT * FROM batch bp INNER JOIN sender_log sl ON sl.id=bp.log_id AND bp.protocol='someprotocol' The second query is used to delete rows: ...
2
votes
2answers
228 views

Limiting the Number of Records Joined

How can I perform a query that contains a (one-to-many) join between two tables, which will only join up to a pre-defined number of joined records? So, lets say I have two tables, one for Matches, ...
0
votes
2answers
41 views

Aggregating results of two database views in one database view

I have a view with name of UserInfo like this: And another view with name of UserRoleInfo like this: I want to aggregate all the records of the two views for one user name like H.F into ...
1
vote
2answers
114 views

JOIN on variable number of columns

I have the two tables courses AND something_about_courses: courses course_code course_session course_type something_about_courses course_code course_session some_description To ensure that I ...
0
votes
1answer
72 views

Merge left outer join column

I have a query that use left outer join. something like that : select issues.id, journal.notes from issues left outer join on (issues.id = journal.issue_id and journal.notes != '') So far it ...
0
votes
1answer
332 views

MySQL query using left join on two inline views not returning rows without values in second view

For some reason when I execute the code below I'm only getting results back that have sku in both views. I thought this should give me everything in the first view and add the content from the second ...
0
votes
1answer
87 views

Low-level relational operators from SQL

I have been asked to outline the sequence of commands using low-level operators (join/project/select) that are used in the following SQL statement; SELECT d.name, k.city FROM DOG d, KENNEL k WHERE ...
1
vote
0answers
86 views

SELECT, PROJECT, CARTESIAN PRODUCT and JOIN

I have the following tables; DOG +----------------------------------------------+ | Name Type Age Kennel_name Owner_name | +----------------------------------------------+ ...
0
votes
1answer
51 views

limiting rows in joins

So I have this problem with one of my queries. The query is meant to get data from table patients and join the table patient_nurse, then table nurses to it. The patients table is as follows id | ...
0
votes
1answer
47 views

What is the correct way of filtering a property by multiple features?

Having the following tables: Property Feature PropertyHasFeature (property_id, feature_id) What is the right way to search properties by specifying multiple features? I want to list all ...
0
votes
1answer
303 views

MySQL: LEFT OUTER JOIN within reason

What I'm attempting to do is LEFT OUTER JOIN a table, but I only want the last inserted record of the joined table to affect the results. Currently each table row within the joined table seems to be ...
1
vote
1answer
125 views

mysql directory grow to 246G after one query, which failed due to table is full

I was trying to run the following statement with the hope to create a join of two existing tables. create table CRS_PAIR select concat_ws(',', a.TESTING_ID, b.TRAINING_ID, a.TESTING_C) as k, ...
1
vote
1answer
194 views

Innodb buffer pool and multiple joins

assume we have 1 Billion records and want to store them in One or Three tables by post_type. post_id -> primary key post_type -> ( page, group, user ) user_id -> index date -> ...
3
votes
1answer
2k views

Postgresql subquery speed much slower than individual queries

In Postgres 9.1. I am attempting to do a single query to get the timezone of a given postal code. I have data loaded in my database, and I am using PostGIS to store the coordinates of each postal ...
1
vote
1answer
2k views

MySQL: NOT EXISTS vs LEFT OUTER JOIN…IS NULL

Is NOT EXISTS or LEFT OUTER JOIN...IS NULL more efficient for finding records in one table that aren't in another? Specifically, I'm trying to figure out which of the two queries below is better: ...
3
votes
3answers
868 views

How to SUM previous sum, e.g N = (N-1) + (N-2) + … + 1?

I have a table name "TABLE_A (id integer, no integer)" . I want to sum "no" with group by "id" and current "sum of no" = previous "sum of no" Here is my code : 1/ Create table & insert data: ...
1
vote
1answer
238 views

Self-join unique pairs

I have a table (players) containing a list of players, I would like to pair up these players in a unique way, so that every player's opponent is unique every round (ie. every time the SELECT query is ...
2
votes
1answer
59 views

Update only the oldest entry in a table with foreign key criteria

I'm working on a forum website. What I am trying to do is updating the thread Title and Content (first post), which resides in different tables - "Threads" and "Posts". "Threads" "Posts" I'm ...
0
votes
1answer
250 views

Nesting inner to sum inner query's result

Suppose I have a query select a,b from xyz The result would be: a        b m1     10 m2     20 m3     30 Can I somehow ...
6
votes
3answers
2k views

Can someone explain why left joining two views in mysql is so slow?

Here is a question I asked yesterday - http://stackoverflow.com/questions/22180727/left-joining-two-views-is-slow. I got a good answer that helped me but I don't understand why the LEFT JOIN is so ...
0
votes
2answers
401 views

25M x 25M inner join (postgresql) performance

I have a one time need to do an inner join of 25M rows on 25M rows. The box is a Alienware area 51, 4 cores 25GB memory and SATA drive (non system disk). So far it has taken 22 hours. I did btree ...
0
votes
2answers
414 views

Select * on inner join with common columns

I have 3 tables (mysql db) on which I want to do an inner join. The problem is that these tables have common columns. I know I could use aliases to differentiate them (select A.x as Ax, B.x as Bx, C.c ...
0
votes
1answer
121 views

Can't get rid of “temporary; Using filesort”

I can't get rid-off "temporary; Using filesort" when ordering columns from the second table explain SELECT * FROM post JOIN post_plus ON post_plus.news_id = post.id ...
1
vote
0answers
448 views

USING to join multiple tables with same field

I have 4 tables, each with a common field QuestionnaireId. I am wondering if there is any difference in output or performance difference between using USING on the field in each join or by specifying ...
0
votes
1answer
78 views

Ask about Inner Join & Union

i want to ask about my script this is doesn't work. i need to help ! SELECT A.*,B.mat_nama,C.mats_nama FROM pengeluaran AS A INNER JOIN(material AS B) ON(A.mat_id = B.mat_id) INNER JOIN(mat_satuan ...
0
votes
1answer
315 views

Get the value of one attribute from the reference key of another table?

I have two tables named as ps_order_detail and ps_product_lang in MySQL. I want to get the product name from one table whose reference key is in another table. I have two tables. First the ...
7
votes
2answers
369 views

Should I nest dependent outer joins in SQL Server?

I have heard mixed information on this and am hoping for a canonical or expert opinion. If I have multiple LEFT OUTER JOINs , each dependent on the last, is it better to nest them? For a contrived ...
0
votes
0answers
50 views

MySQL - query join returning zero recs from table with data

I've provided a file that has the table structure and some sample data that I'm working with. I don't understand why I'm getting nulls from a joined table, where there is data. Here's my query ...
0
votes
0answers
66 views

Equivalent of old style join with new style

Can someone please help me write the following join expression in new style: Select tb1.col1,tb2.col2 from table1 tb1, table2 tb2 where tb1.col1>=tb2.col2 I know that the equivalent of ...
2
votes
2answers
17k views

SQL Update column with data from another table

I am working on complicated problem, but I will simplify it to this problem. I have two tables A [ID, column1, column2, column3] B [ID, column1, column2, column3, column4] and i want to update ...
0
votes
0answers
201 views

Alternatives for subquery

There are three tables: product_hits, products, and product_subcategory_map. I want to count the number of product_hits and for each product. There could be more than one subcategory in the ...
0
votes
1answer
61 views

MySQL: join query

I've got the following two tables: mysql> DESC domains; +-----------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra ...
3
votes
1answer
155 views

postgres filtering select based on combination of joins

I am having trouble filtering a request that depends on a combination of child elements (one-to-many relationship) Please consider the following example. CREATE TABLE sample_container ( id serial ...
12
votes
1answer
312 views

Why does subquery use parallelism and join doesn't?

Why does SQL server use parallelism when running this query which uses a subquery but it doesn't when using a join? The join version runs in serial and takes around 30 times longer to complete. Join ...
3
votes
2answers
442 views

cross database way to force join strategies

[how to enforce the query to use certain join algorithm] Knowing that there are several joining algorithms [Nested Loop; Sort Merge; Hash Join], when implementing a query , is there any technique to ...
0
votes
1answer
90 views

Would it be better to do a sepparate query instead of a left JOIN?

Only a couple of rows is returned when not using LEFT since there isn't always data in the associated table - recipe_preparation. This is one of a couple of tables with the same "issue". SELECT r.id, ...
1
vote
2answers
179 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) ...
5
votes
1answer
2k views

Can I provide a default for a left outer join?

Suppose I have tables a (with column a1) and b (with columns b1 and b2) and I perform a left outer join SELECT * FROM a LEFT OUTER JOIN b ON a.a1 = b.b1 Then b1 and b2 will be NULL where a value of ...
0
votes
0answers
276 views

Alternative to TEMPORARY tables capable of re-opening in a query?

I use TEMPORARY table for calculation of temporary data, but TEMPORARY tables in mysql has a big limitation, which made it useless for me. A table cannot be re-opened in a query. This mean I cannot ...