SQL term used to describe when a `SELECT` statement is used as part of a larger SQL statement. The larger statement may be DML and is always found within brackets or parenthesis.

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MySQL Subquery Returns Null In Stored Procedure, Works Fine In Query

I have a subquery in a MySQL Stored Procedure where the value returns null even though the data is clearly there. Pulling the subquery out and running it works fine. I've checked the parameter values ...
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65 views

Select highest id of each type in mysql

I am creating a database that keeps track of backups on our various servers. The query that I am using actually seems to work for the most part. The only issue is that it isn't getting the highest ...
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137 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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2answers
47 views

How to optimise MySQL query that uses dependent subquery

I have a web app that has a custom feed of images. The image queried are based on whether the users have previously seen the image and ordered by a Hacker News style score. There are only 1000 rows ...
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71 views

Why is the subquery apparently correlated? How to avoid it?

I have a table orders and a table orderpositions. The orderpositions (basically the items bought with the order) are linked via orderid (indexed) to the orders primary key. For a given set of orders ...
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6k views

MySQL: Delete all but last N records

Consider the following table: mysql> DESCRIBE pixels; +---------------+-------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default ...
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41 views

Is it more efficient to union from sub-query or combine two outer queries?

I searched for this but couldn't find the response I needed. So my apologies if this has already been asked. I'm asking in regards to DB2 but I suppose this would apply, generally speaking, to just ...
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206 views

Very slow update with subquery (different tables)

I run this query to update "domains" table based on "log" table: UPDATE domains SET domains.mx_collected = 0 WHERE domains.domain IN (SELECT log.mail as domain_name FROM log WHERE `time` >= ...
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22 views

mysql - select random rows with max 3 rows per parent id

I currently have a query that returns a maximum of 3 rows per parent_id. I want to enhance the query to return a maximum of 3 random rows per parent_id. This does not work for me at the moment as it ...
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51 views

Use array expression from subquery in ANY() condition

I have a relatively complicated query with a subquery fetching an array like so: ... ARRAY(SELECT category_id FROM category_schedule_con con WHERE s.id = con.schedule_id ORDER BY category_id) ...
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30 views

Update row value with a sub-select join

I am trying to update 1 column in all rows in a table to have an appropriate count value. Sadly, the SELECT query I am using won't let me join on a field in update table. The query looks like this ...
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52 views

Subquery returned more than 1 value. please help. i beg for mercy

This is may table. In one column there are daily dates and in the other is a classification. I use this query to count how many registers are in a month and which ones are C or D, but the subquery ...
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55 views

Optimize query or split in two queries and process result separately?

I have this DB schema: As you may notice already there is no relationship between tables and won't be on the future. If I run the following queries I will get a lot of rows per table: SELECT ...
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109 views

Subquery on timestampdiff only allows for 1 result, how do I scale this for all results?

I'm currently writing up a query which is meant to output data to show curves of power profiles, and I'm facing a slight problem. So far, I've managed to do this: select datetime, PLANT_STATUS, ...
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2answers
173 views

#1093 - You can't specify target table 'R' for update in FROM clause

As an attempt to answer Difference data between adjacent rows UPDATE Visits R SET Duration = TIMEDIFF( ( SELECT ReqTime FROM Visits N WHERE N.ID > R.ID AND N.Session=R.Session ORDER BY ID ...
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111 views

How to rewrite subquery to return only 1 row

I need to somehow check if query result is NULL, MySQL returns error Subquery returns more than 1 row. How should I rewrite it in order to work correctly please? SELECT DISTINCT user.id, ...
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7k views

SELECT LIMIT 1 per column value?

Lets say I have the following table ----------------------------- | user_id | comment | ----------------------------- | 2 | thats cool | | 2 | awesome | | 3 | ...
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26k views

SELECTing multiple columns through a subquery

I am trying to SELECT 2 columns from the subquery in the following query, but unable to do so. Tried creating alias table, but still couldn't get them. SELECT DISTINCT petid, userid, (SELECT ...
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3answers
233 views

No advantage of using Cross Apply or CTE over inline sub-query

I came across a query like this: SELECT (SELECT COUNT(1) FROM Orders o WHERE i.ItemId = o.ItemId) [C] FROM Items i I changed it to following ;WITH cte_count AS ( SELECT COUNT(1) c, OrderId ...
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2answers
53 views

Need some assistance on MySQL Sub query

I have a table in MySQL. The table structure is as follows. id | emp_id | call_start | call_end | call_type -------------------------------------------------------- 1 | 20043 | ...
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1answer
92 views

Subquery magic in PostgreSQL

I have a query: update product_product set (write_date, default_code) = (LOCALTIMESTAMP, 'update') where product_tmpl_id in ( select distinct product_tmpl_id from product_template ...
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1answer
54 views

Why conditioning before and after join, gets different results?

I want to left join two tables and then return some of the records. My first query was: SELECT * FROM card LEFT OUTER JOIN user_card ON card.id = user_card.card_id WHERE card.package_id =14 AND ( ...
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40 views

Join Two queries with different declarations

I need to join two different queries to get some columns from both. The first one has a CTE. Query1: WITH StatusChanges AS ( SELECT HistoryID,PartID,Status, DateAdded, ...
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3k views

Oracle 10g: Optimizing an update query that uses a subquery

I have the following query within a stored procedure, and I've been trying to improve its performance to no avail. UPDATE TBL_REPORTING REP SET (REP.ISSUER_ID, REP.ISSUER_NAME ) = ( ...
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31 views

Lookup multiple ids in seperate table with 2 subquerys

I have a query from a timesheets tables that I am using to select a submitter, approver, and a date. SELECT PRTIMESHEET.POSTED_TIME, PRTIMESHEET.PRRESOURCEID as "SUBMITTER", ...
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99 views

Should I use a subquery to help SQL Server find the correct plan

I have a query (which has components which are built on the fly depending on the selections a user makes in the interface) that runs in SQL Server 2008-R2 that runs in about 100 databases. Users are ...
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31 views

Delete using join or using sub-query?

I need to delete rows from a table based on what is present in a temporary table. For me, both of these statements work : DELETE from main_table where `id` in (select `deletable_id` from ...
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53 views

Problem forming a query with subqueries in design view? (MS Access 2010)?

I just started a new job as a dbase admin intern, and due to the database being very large, it is better to do queries in design view, rather than hardcoding the sql. That being said, I cant seem to ...
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86 views

How to organize long Query

I have a massive query string that I am trying to pick apart for a project I am working on. I am looking for some guidance on how to take it apart(format it into human readable). Also, what are the ...
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31 views

subquery in set clause retrieving different values

I want to update the column "kstplcode" using different values coming from column warehouse except the value "main" with their corresponding delivery numbers. I've tried this code but the set clause ...
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2answers
61 views

How to access row value from UPDATE sub query function?

I would need to use UPDATE like this: update offer set (bank, bank_id) = (cost, gid) from ( select cost, osm_points.gid from pgr_kdijkstraCost( 'SELECT gid as id, source, target, walk_cost as cost ...
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2answers
40 views

Which query performs better when searching a row where a column has maximum?

Consider a simple table for example purposes: person(name varchar, age int) I have a task to retrieve the oldest person. Which query is better in general for such problems? Query 1: criteria with ...
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23 views

How to subtract records from a table based on their existence in another

I have an Access 2010 table Assignment key Empl Number key Year Number key Week Number key Proj Number It assigns employees to zero or more projects for given work weeks, thus, all ...
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34 views

Spatialite: use of virtual spatial index for distances

I'm currently learning to use spatial access methods for query optimization. I'm going through the examples in spatialite cookbook and got stuck in here ...
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35 views

Passing filter params to a sub query

I'd like to create a view from the query below, but the query contains a sub query which I need to apply a filter to (the place is marked with a comment). I'm wondering if it's possible somehow to ...
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1answer
183 views

How to union four different tables

I have two tables whereby both of them use sub queries. These two tables are combined by using UNION ALL. I have two other tables that only uses a WHERE clause and both of these are combined using ...
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1answer
62 views

Select records as groups based on sequence and date

I have data stored as: CompID | Seq | Udate | Utime --------+-----+-----------+------- mx433 | 1 | 1/1/2012 | 13:54 mx433 | 1 | 1/2/2012 | 13:43 mx433 | 2 | 1/4/2012 | 14:23 mx433 ...
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23 views

In MySQL, get number of pregnant women who received 3 ANC checkups

I am working on a project where it is required to find out the total number of pregnant women who have received 3 ANC(Ante-Natal Care) checkups done. A pregnant women is said to receive 3 ANC ...
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2answers
61 views

Insert query with a subquery

I want to insert somewhere around 400 rows into a table. All of the column values will be the same fixed value for most of the columns, with exception to one column which I want to pull from a fairly ...
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46 views

Smallest unique string among multiple columns

Somewhat similar to the Largest Common Substring (http://en.wikipedia.org/wiki/Longest_common_substring_problem) I'm trying to find the smallest unique string from a table. In some tables, its just ...
2
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1answer
4k 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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1answer
48 views

Using a subquery in a LIKE statement

I need to write a subquery inside a LIKE statement. This subquery would return me a word that I need to find in the middle of a sentence (that belongs to another field). Is it possible? This is how ...
4
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1answer
130 views

Combine multiple queries into 1 query

I have a message table in Postgres 9.4 that contains a words field of array type, with random words of a message. Currently I have millions of messages: \d messages Table ...
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3answers
536 views

Check if any of the values is in a subquery result

I have a complicated subquery that returns a list of order IDs. I need to get a list of customers who have these orders. The problem is that there are two ways of assigning a customer to an order (one ...
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94 views

Call function where argument is a (sub)select statement

My function takes an int4 as argument and returns a table: SELECT * FROM test_function(545421); -- works fine SELECT * FROM test_function(SELECT customerid FROM tableX ...
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52 views

Indexing on cached data from related table using triggers — Is there a better way?

Edit: Schema details per request from Aaron Betrand -- I'll break the schema down to the relevant fields of the two tables. Orders (ID int IDENTITY, Status char(1)) Services(OrderID FOREIGN KEY ...
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100 views

Amazon Redshift: “*SELECT* 1” vs. volt_dt_0 vs. volt_tt_51343b6aa3bd4

I've noticed subqueries in Amazon Redshift can be represented in the explain plan in 3 separate ways: -> XN Subquery Scan "*SELECT* 1" -> XN Subquery Scan volt_dt_0 -> XN Seq Scan on ...
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29 views

Subquery optimization

I was reading through this article - http://explainextended.com/2009/09/18/not-in-vs-not-exists-vs-left-join-is-null-mysql/ I am working with an existing design. What I want is to be able to select ...
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1answer
52 views

on every row on SELECT Query must lookup to other table

I'm working on Login/Logout System and I'm facing this problem regarding on SELECT Query. I have 2 tables namely dtr_tbl and shift_tbl. In dtr_tbl are the logs of the user(login/logout time details) ...
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81 views

Alias of Subquery not working

I have been trying to get an order by to work correctly with an aggregate function. i.e. order by (bp + points) I also try adding these as a total amount from the following query however. If I try ...