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

learn more… | top users | synonyms

2
votes
1answer
631 views

Help with a complicated MySQL Query inserting data using select from 2 tables

I am stuck with a case and unable to get the desired result from my query.. I have to insert into a table some records based on multiple records from 2 different tables.. Tables: Target: ...
1
vote
2answers
908 views

Table orders regarding Nested loop join in DB2

First I would like to cite the existing post Table order in Join Query so the author is saying that the table order really doesn't make things(result, access plan)different. I have doubt on this ...
1
vote
1answer
2k views

Really slow DISTINCT ON query with multiple joins

Originally posted: http://stackoverflow.com/questions/11173717/expensive-query-on-select-distinct-with-multiple-inner-join-in-postgres The songs table has only about 4k rows, posts and stations have ...
1
vote
3answers
72 views

How can I query to do this?

I have 2 tables, in feeds I have my feeds and (feeds.ID) is the primary key. second table is items. and feeds.ID is realted to items.feed_ID, so with a simple inner join i can extract the data of each ...
3
votes
2answers
8k views

forcing Oracle to use hash join for a subquery

I have a query that looks like SELECT * FROM table0 WHERE id IN (SELECT id FROM table1 JOIN table2) Oracle is choosing to join table0 with the result of (table1 x table2) using nested loops and ...
1
vote
1answer
852 views

Merge multiple table output but indicate which tables the records came from

I have an application with a function that uses a stored procedure (SQL Server 2008 R2) to pull in and arrange data from one table. Now, I’ve been asked to make it pull from two tables, but it’s not ...
1
vote
1answer
3k views

Combine column from multiple rows into one row in SQLITE

I have a sqlite-database with the schema Articles Id Name Tags Id Name ArticlesTags Id ArticleId TagId I´m trying to query for Articles.Name and a LIST of tags. Basically what I would want ...
0
votes
1answer
40 views

Linking table or column key

Simple structure: have a table PAGES - which stores information about specific landing pages working on developing a GROUPing concept for the pages, where we are saying that a page may or may not ...
2
votes
1answer
226 views

Rewriting a query and eliminating subqueries

I have the following query : SELECT ws_id, n50, num_singletons, num_segments_less_100, kmer, num_all_reads, number_bases_in_contigs, num_bases_in_singletons FROM stats_assembly WHERE ws_id IN ( ...
0
votes
2answers
71 views

I couldn't compile this little query (needs 2 tables)(mysql) [closed]

i have 2 tables as like seen : user table : id, userid , country friends table : id, userid , friendid so i want to get friendid rows from friends table where friends.userid == user.userid and ...
3
votes
1answer
669 views

How to order query results by tag weight in IN('tag1', 'tag2', 'tag3')

Consider a simple query as SELECT * FROM posts JOIN tags USING(post_id) JOIN tag_map USING(tag_id) WHERE tags.tag IN('tag1', 'tag2', 'tag3') tag_map is a many-to-many relationship between tables ...
1
vote
1answer
2k views

What joins are available in Informix 9.2?

I'm testing some queries with an old version of Informix (9.2.1) and can't seem to execute even the most basic queries containing RIGHT OUTER JOIN or FULL OUTER JOIN. Tried several variations (RIGHT ...
1
vote
4answers
482 views

cross self join to get more rows - better solution?

I have a table employees: +----------------+------------------+ | Field | Type | +----------------+------------------+ | id | int(10) unsigned | | persons_id | ...
1
vote
3answers
201 views

How is a join performed by a database engine?

How is a join between two tables actually performed by a database engine? I am sure that listing one tuple against all tuples of the other table cannot be the way to perform the join; it's just a ...
1
vote
1answer
434 views

Finding Duplicates in LEFT JOIN

Here is my table structure: create table table_a (emp_name varchar(100), dept_name varchar(100)); insert into table_a values ('amar', 'finance'); insert into table_a values ('akbar', ...
5
votes
2answers
1k views

Index on primary key not used in simple join

I have the following table and index definitions: CREATE TABLE munkalap ( munkalap_id serial PRIMARY KEY, ... ); CREATE TABLE munkalap_lepes ( munkalap_lepes_id serial PRIMARY KEY, ...
2
votes
2answers
2k views

Improving performance of nasty nested-view joins

I have a moderate-sized database spread out over a few tables, the rough architecture is: Input Data (Data ID, Session ID and a few fields of statistical importance) Input File (Data ID and a blob) ...
1
vote
2answers
2k views

LEFT JOIN conversion to INNER JOIN, can't change FROM clause

I have 2 tables: BASE is master and is linked with CHILD via field ID: Left outer Join / 1:N relation. These 2 tables contain historised data, defined by 2 date-fields: start_date and end_date. ...
3
votes
3answers
495 views

SQL JOIN Syntax in MS SQL

I have been taught in my MSSQL classes, this is how to join two tables select * from FirstTable A JOIN SecondTable B on A.ID= B.ID Now in my professional life, I came across JOIN queries like ...
7
votes
1answer
248 views

Table order in Join Query

if i say: Table1 left join Table2 is it the same as saying Table2 right join Table1 ? In other words, should i expect to get the same results from 2 identical queries where the only thing that is ...
2
votes
1answer
765 views

Is it correct, order of where clause doesn't matter when it is used with join?

I have question on execution of queries in which join is used with where clauses. I read this question on join with where conditions. I tried options like disabling rules and checked actual query ...
1
vote
1answer
65 views

Joins in MySQL database

I am a newbie to the MySQL database.I want to know different types of joins in MySQL and any link or any other kind of documentation with examples which will clear the doubts will highly appreciable.
4
votes
1answer
5k views

mySQL query optimisation — multiple joins or select … where not in (select distinct…)?

Background I have a Drupal install accessing a large users database (~200k rows) and my "People finder" functionality needs to access all those rows (in a random order). I don't seem to be able to ...
3
votes
2answers
8k views

How to combine UNION and INNER JOIN?

I'm fetching the grandparent of all nodes in a tree as follows: SELECT P.id, P.parent, GP.parent gp_id FROM product_groups P INNER JOIN product_groups GP ON P.parent = GP.id There is ...
6
votes
3answers
4k views

Why is this Full Outer Join not working?

I've used Full Outer Joins before to get my desired results, but maybe I don't fully understand the concept because I am not able to accomplish what should be a simple join. I have 2 tables (which ...
3
votes
2answers
375 views

How do I calculate working business minutes?

I'm working on business inteligence reports and one of my task is to create reports for time tracking. I have to report on business minutes (10 hours per day) within business week (monday to ...
1
vote
1answer
72 views

How can this data be joined?

Definition: table_A table_B id,description id,description,id_table_A Column id_table_A is a foreign key to the primary key of table_A and is not mandatory. Sample data: ...
3
votes
1answer
4k views

Having trouble with Merge Join with SSIS

I am currently using Merge Join to perform an inner join on two sorted sets of data in SSIS. The problem I am having is that no records are being returned from the inner join. To troubleshoot I have ...
2
votes
1answer
413 views

Query takes hours

Up until now all queries in my PostgreSQL application were fast. During the last days, sometimes a query takes several hours. Index are healthy, because after dump, restore, vacuum -z, it is still the ...
2
votes
2answers
525 views

Joining based on date (or date range)

I'm not sure if I've completely fudged the design of my small hobby database (I'm not a DBA by any means), but I have a table like this (primary key is (staffid, effectivefrom)): staffid | target | ...
1
vote
1answer
641 views

Usefulness of Foreign Key WITHOUT reference option

Sorry, if this is naive question, but I searched a lot and did not get a vivid answers. Consider a simple InnoDB FOREIGN KEY without ON DELETE or ON UPDATE I think this will avoid INSERT of a value ...
2
votes
2answers
2k views

Limit WHERE to MAX() & COUNT()

This is my current mySQL query: SELECT e.*, MAX(m.datetime) AS unread_last, COUNT(m.id) AS unread FROM TAB_EVENT e LEFT JOIN TAB_MESSAGE m ON e.id=m.event_id WHERE ( m.`read` IS NULL OR ...
5
votes
2answers
574 views

Unexpected extremely long query time (~5 minutes using nested WHEN-INs)

For the first time, I am running up against a horrifically long execution time of a MySQL query (~5 minutes). The data in the database is highly (and not arbitrarily) normalized. It very efficient ...
2
votes
2answers
168 views

Validation of availability for a new order

I have a management application of sales, stock and payment on a warehouse whole saler from a web interface. In particular, when a order is effectuated it must create a line corresponding to each ...
2
votes
3answers
388 views

Express union which is dependent on other results

I would like to make a union of two tables that are actually in a hierarchical constellation. How would I write that in relational algebra? Say table A is the parent of B in a 1:n relationship. ...
0
votes
1answer
4k views

Oracle SQL for left outer join to rownum = 1 of another query?

Background I have a query joining many tables together, the chief of which is a workorder table. I also have a table called WOStatusHistory, which stores every status for every workorder. A diagram ...
6
votes
3answers
262 views

What does the output of a JOIN statement look like?

I've been wanting to use joins for a while, but I'm having trouble visualizing the output so I know how to put it to use. Let's say I have 2 tables: CREATE TABLE Cities ( id INT UNSIGNED PRIMARY ...
2
votes
2answers
1k views

Update column by comparing date and string values together

I have problem in updating table. I need to update table by comparing date and name with another table. I have two tables: table 1 : dim_sesid name(varchar) role ...
7
votes
3answers
1k views

Oracle's left join and where clauses errors

CREATE TABLE "ATABLE1" ( "COLUMN1" VARCHAR2(20 BYTE), "COLUMN2" VARCHAR2(20 BYTE) ); CREATE TABLE "ATABLE2" ( "COLUMN1" VARCHAR2(20 BYTE), "COLUMN2" VARCHAR2(20 BYTE) ); ...
2
votes
2answers
442 views

get column from too many tables in mysql

.I have too many tables X1,X2,...Xn (they might exceed 75 tables) in Mysql DB to represent departments of a very large company. every table has structure something like this desc X1; ...
1
vote
1answer
162 views

How should row-specific metadata be created handled for an outer join view?

I have two tables, a large (millions) table of Tickets for orders, and a small (hundreds of thousands) table for Invoices metadata on a subset of those tickets. The metadata is information about when ...
26
votes
8answers
22k views

What is the difference between an INNER JOIN and an OUTER JOIN ?

I am new to SQL and wanted to know what is the difference between those two JOIN types? SELECT * FROM user u INNER JOIN telephone t ON t.user_id = u.id SELECT * FROM user u LEFT OUTER JOIN ...
4
votes
3answers
393 views

How can I select all online friends?

I'm currently working on a social network software written in PHP & MySQL, and it's all pretty fine, but one thing I'm stuck about is online friends. My tables looks following Users ...
10
votes
3answers
4k views

Should I use SQL JOIN or IN Clause?

I have a question about best approach. I am not sure which approach is best when data is considered variable in size. Consider the following 3 TABLES: EMPLOYEE EMPLOYEE_ID, EMP_NAME PROJECT ...
2
votes
1answer
6k views

Using multiple PIVOTs JOINs and GROUP BYs for advanced report generation

I've developed a timesheet recording system, that allows users to record: A Period of time (9:00 to 12:00) What they did during that time (DutyActivity: 1 hour report writing, 2 hours training) ...
2
votes
1answer
298 views

Postgres planer JOIN removal

I have two tables, one contains a lot of rarely update data, and one contains a little of frequently update data. Every record in second table has corresponding record in the first, like following: ...
1
vote
3answers
2k views

Grouping results to get unique rows after multiple joins

this is my first question on dba.stackexchange, hopefully it will be worth it. I am usually a bit more active on Stackoverflow as I am a developer. disclaimer : I don't have full control over the db ...
1
vote
1answer
354 views

Simple select statement not returning correct data

I am trying to return data, where I want the item name (items.name), vendor name (vendors.name), url of the price (prices.url), and the price (prices.price) from 3 different tables (items,vendors and ...
8
votes
2answers
4k views

SQL Server Join/where processing order

After reading Slow SQL query, not sure how to optimize, it got me thinking about the general performance of queries. Surely, we need the results of the first table (when other tables are joined) to be ...
6
votes
1answer
639 views

Why can't we perform joins in a distributed database like Bigtable?

From this answer to What database does Google use?, BigTable is not a relational database. It does not support joins nor does it support rich SQL-like queries. Is this obvious? I do not ...