A core SQL statement, SELECT retrieves data from one or more tables or other sources of row set data such as views or table-valued functions.

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MySQL: Join one Row in a table with two Rows in other table

In my MYSQL Database COMPANY. I have two tables, like below in my diagram (arrow shows relations): `users` `user_login` +--------------+ ...
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Order by on an alphanumerical column

I have a column that has strings of the following type: Miller 10 Allen 20 King 10 .... Jones 100 I try to sort the column based on the numerical part of the data. I tried the following: SELECT ...
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Get Hierarchial Data in Self-Referencing Table (Parents , Childs) [closed]

In the following Fiddle, sqlfiddle I will pass a sno and I need all the parents of that sno in a table. And all the children of that sno in another table Please refer to this question. Since ...
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2answers
516 views

Select query having count and variable

I have a table like the one below. I need to form a select query. I'm going to pass a RefID like SELECT SNo FROM Register WHERE RefID = 1 And beside the SNo in the Statement, I need to have ...
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2answers
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How to JOIN two table to get missing rows in the second table

In a simple voting system as CREATE TABLE elections ( election_id int(11) NOT NULL AUTO_INCREMENT, title varchar(255), CREATE TABLE votes ( election_id int(11), user_id int(11), FOREIGN KEYs for ...
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1answer
321 views

Insert from one row to another using cases

My original table was(being used since 2005): CREATE TABLE `request` ( `msg` VARCHAR(150) NOT NULL, `id` VARCHAR(20) NOT NULL, `ctg` VARCHAR(10) NOT NULL DEFAULT 'misc', `date` ...
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2answers
2k views

SELECT TOP in MySQL

How can I do this in MySQL? SELECT TOP 50 PERCENT * FROM table What's the simplest way to do it without running to separate queries (if possible)?
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1answer
66 views

PostgresSQL: Get single attribute of UDT in SELECT statement

I created a user-defined type in a PostgreSQL 9.2 database and am trying in the SELECT statement to get only an attribute of the UDT. However, I don't seem to get my code to work. Creation of type ...
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1answer
491 views

Selecting minimum value using a subquery

I need to write a query to grab the lowest price from each merchant and output the price link (p_link) and some other information such as merchant name + rating. We have a table for prices ...
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1answer
108 views

Search within same ID accross several rows

My table has the following structure: +----+---------+------------+-------------+ | id | word_id | meaning_id | sentence_id | +----+---------+------------+-------------+ | 1 | 1 | 15333 | ...
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6answers
11k views

Is it possible to mysqldump a subset of a database required to reproduce a query?

Background I would like to provide the subset of my database required to reproduce a select query. My goal is to make my computational workflow reproducible (as in reproducible research). Question ...
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2answers
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oracle - list users with access to certain tables

I'm sure this has been asked before but I can't seem to find the relevant details for the following. Is there some sort of pre-built table that can do the following (I have used dba_tab_privs but it ...
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279 views

Need a way to query a table, and JOIN it with the TOP 1 related record from an other table

As a follow up to this question, I'm wondering if there is a better and/or more efficient way to gather the data in question. As stated, this query does return me 95% of the data I need -- SELECT ...
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384 views

Should I use select count(*) for counting records or having a field like comments_no for tables like post, comments?

In my recent project which is about social networking for an Asian country, I'm in doubt whether I use the below SQL statement for counting records: SELECT COUNT(id) shareLikeNo FROM ...
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2answers
361 views

SELECT only values THAT are different

I have two instances user1 and user2. They have colors u_id | color<br> 1 | red<br> 1 | green<br> 2 | red<br> 2 | blue<br> I need a mysql request, that ...
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2answers
3k views

Can someone explain why select with nolock will query a potion of updated data?

I was reading the answer from here (from stackoverflow, I think should ask in here) NOLOCK means placing no locks at all. Your query may returns portions of data as of before UPDATE and ...
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2answers
424 views

MySQL Reusing calculation in SELECT clause in a VIEW

I have an SQL query that has a simple date difference between NOW() and the creation date (is in the table). I need to reuse this again within the SELECT clause in a VIEW. Is this possible at all? ...
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1answer
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MySQL Insert into two tables using new IDs

I'm trying to select data already in the database and insert it into two tables using the generated ID from table one. table1 contains configuration options, table2 contains pricing data. Table2 uses ...
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3answers
845 views

Count consecutive rows in mysql

I would like to get the count of consecutive rows in MySQL. It is a large database I try to avoiding the joins. Here gadget_id means vehicle and every 20/30 second the vehicle sends the current ...
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1answer
186 views

Does the order of fields in SELECT query matter when using composite indexing?

I understand that the order of columns in the index itself matters immensely; however, what about the order of columns in the subsequent SELECT queries that make use of that index? For example, if I ...
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3answers
135 views

Tuning reads (or perhaps the truncate!) for unusual database structure requiring regular truncates

We have an unusual database structure (I leave the reasoning for another question), that in it's current form requires a regular truncation and recreation of allot of row (about 1 million). We're ...
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2answers
1k views

Getting repeated value in a group_concat only if ids are different

I have two tables, first the table Product: id|category_id --+----------- 1 | 12345 2 | 12345 3 | 12465 And then a table activity: id|prod_id|activity_type |description ...
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2answers
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How to cast an integer to a boolean in a MySQL SELECT clause?

I'm new here so be kind to me. I have the following scenario: I have many tables which, for the sake of simplicity, are represented in a View in my MySQL database. My problem is that I need a value ...
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1answer
249 views

How to re-arrange rows to best fit within groups?

I categorized a table with the method introduced here to categorize my items to folders with a limit size of 100. mixing_order id num_items cat order_in_cat cumulative_sum folder 1 ...
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1answer
84 views

Select columns from 4 tables

First thing, I am totally new to SQL. I saw some tutorials, videos, tried searching but didn't find what I needed. I know it has asked before, but I couldn't find it. What I need to find is basically ...
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1answer
159 views

MySQL SELECT query: i want show duplicated entries

Example My query is: SELECT code_CAT FROM categories WHERE id_code IN(14,14,14,14); output is: 53724 Only one row. Instead I want this output: 53724 53724 53724 53724 How can I achieve ...
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158 views

Inner Join or direct data save in SQL Server

I am developing a social network site and expecting very good response from people so expecting huge users (maybe more than million in years). My website is holding user information table and all its ...
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1answer
3k views

Multiple “GROUP_CONCAT”s with WHERE clause

In a table as id name type info 1 BMW car yes 2 Reno car no 3 IBM electronics no 4 Sony electronics yes 5 Mazda ...
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2answers
494 views

How to mix pairs of rows without JOIN (in a temporary table)?

I have a TEMPORARY table containing pairs of key/value as id col1 col2 type pair 1 key1 key2 key 1 2 value1 value2 value 1 3 key3 ...
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1answer
327 views

Retrieving a fixed range of rows from Postgresql

I have a query: select qid,ansid,ans from table1 where askerid='something' This query can retrieve many rows. But I want to display only 50 rows at a time and then if the user clicks on more, the ...
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1answer
1k views

Simple Oracle query hangs depending on WHERE clause

Not used to using Oracle, but we have a large database where a non-unique query like SELECT * FROM employees where department = 'HR' is working, results list up no problem. But when I do ...
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1answer
1k views

MySQL Explain: Using index, using temporary, using filesort. Can this query be improved?

I'm working on a event tracking system which uses a handful of lookup tables as well as the primary logging table. In a report I'm writing, an object can be selected to view statistics against. The ...
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USING construct in JOIN clause can introduce optimization barriers in certain cases?

It was brought to my attention that the USING construct (instead of ON) in the FROM clause of SELECT queries might introduce optimization barriers in certain cases. I mean this key word: SELECT * ...
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217 views

SELECT multiple sensor values in one query

Background I have a couple of devices, each with a couple of sensors. I log these every now and then and stores them in a table described below. When someone requests a web page, I fetch a couple of ...
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616 views

MySQL error in where clause : Unknown column

When I try to execute the query below, I receive the error message: Unknown column 'have_discount' in 'where clause' My query is: SELECT DISTINCT(MP.item_id), item_title, item_user_id, ...
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1answer
602 views

Select fields from multiple tables

I want to make a query a little complicated, and I'm not able to do it alone. I have the following tables: Table color: id_uo P id_cor PF id_area F text_cor Table area: id_area P ...
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1answer
86 views

JOIN 2 tables, and query data from them 3 times

Basically I have 2 tables: post_meta and posts. post_meta has a post_id, key and value: post_id key value 6343 make Chevy 6343 model Volt 6794 make Chevy 6794 model ...
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1answer
990 views

I have to update all the rows of a Column in a table. Here is my query

So My tables are People: People_name(VARCHAR 100), People_id (INT, PRIMARY KEY AUTO INCREMENT) Tracks: Track_id(INT PRIMARY KEY), People_id_references (int ,Foreign key references ...
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mysql select query optimization [duplicate]

Possible Duplicate: mysql select query optimization I have two tables, testa and testb. CREATE TABLE `testa` ( `id` INT(10) NOT NULL AUTO_INCREMENT, `name` VARCHAR(50) DEFAULT NULL, ...
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Is it always bad to use SELECT * FROM?

It is widely recommended NOT to use SELECT *. I understand this, as it is not a good idea to bring the entire row into memory, when only a few cells are needed. Is it still bad to use SELECT * when ...
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5answers
264 views

How define select, if bridge pair may have 3 players?

Normaly a pair has 2 players, but if there is an odd number of players at the club, one 'pair' has 3 players. Table, members: pair, player_id 1 1 1 2 2 3 2 4 3 5 3 6 4 7 4 8 5 9 5 10 6 11 6 12 6 ...
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2answers
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HELP with SQL WHERE syntax

I have to pull out a range of entries of a database, all based around two pieces of data. In itself thats fine. An example of the data is: Record ID Tags 1 1423 Day, Sun, Warm 2 ...
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2answers
9k views

Select column names whose entries are not null

I would like to have a list of those columns of a table that have at least one not-NULL data entries in them. In other words, I would like to get the column names for which the following returns at ...
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1answer
256 views

Tricky selection of grouped rows, selecting based on values of two distinct but related rows

Say I have a table with the following information (sorted here for display purposes) taskid | reference | centreid | date_out --------------------------------------------------- 10001 | ...
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2answers
2k views

GROUP BY two columns

I want to count two columns, but need to get the results of first column in one row. SELECT country, COUNT(*) FROM table1 GROUP BY country, type This query gives me country type COUNT(*) ...
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1answer
291 views

Select consecutive number of rows starting from some number

What I need is to select 100 consecutive rows from a table, starting at some defined point without ordering data. As far as I can observe, inserted data to a table is stored in no order but is ...
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1answer
658 views

How to COUNT number of rows with LIMIT?

I want to catch X rows, thus, I set LIMIT X; but how can I simultaneously count the total number of rows too? Currently, I use two separate queries to do so as SELECT COUNT(*) FROM col WHERE CLAUSE ...
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MySQL: SELECT the n-th item from an ordered result

SELECTing the top n elements from a table is easy: SELECT id FROM pixels WHERE pixel_id='some_pixel_id' ORDER BY id DESC LIMIT 1000; Finding the n-th element with a subquery is quite ...
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1answer
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Oracle error “too many values”, must be solved with nested SELECTs

I have hit upon a "too many values" error in Oracle, when working with some intricate nested SELECTs. A simplified description of my problem, on a toy problem describing the hierarchy in a company. ...
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1answer
378 views

Select one name per person where spelling variations exist

I have a source table that contains Employee IDs and names. The employee names may be listed multiple times with variations on the exact spelling (see 'source table' for example - note the middle ...