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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1answer
4k views

Getting unique names when the IDs are different (DISTINCT ?)

I've got this table: id | name 1 | John 2 | John 3 | Peter 4 | Mike 5 | Mike And I want to get the unique names, getting the latest one in the list. I could go for: SELECT DISTINCT name ...
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5answers
197 views

Find all values not present for other values of other column

Let's suppose I have a table with integer columns a and b (each pair (a,b) is unique) and following data: a | b ------- 1 | 2 1 | 3 1 | 4 1 | 5 2 | 1 2 | 3 2 | 4 3 | 1 3 | 3 Now I need to ...
3
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2answers
2k views

MySQL: Is it possible to order a query by a specific letter using ORDER BY?

What I'd like to do is order my query so that the results show every row found, but are ordered by showing results that begin with the letter 'D' first. Is this something that is possible to do with ...
3
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1answer
278 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 ...
3
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1answer
897 views

Index on foreign key makes query extremely slow

We are recently experiencing a tremendous query slowdown with spilled over temp tablespace. A specific query causes this problem. The queried table (table3) has an indexed PK, three FK with indexes ...
3
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1answer
5k views

Error “column does not exist” in a SELECT with JOIN and GROUP BY query

I'm using PostgreSQL 9.1 with a Ruby on Rails application. I'm trying to list the last version of each "charge" (in my history table : hist_version_charges) belonging to the same project id ...
3
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1answer
2k views

Any disadvantages of “SQL_BUFFER_RESULT” for MySQL SELECT?

I've been researching the usage of SQL_BUFFER_RESULT. Mostly it is referred to as an aid to reduce table lock issues. It seems to be a good option to use. However I cannot seem to find any ...
3
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1answer
526 views

Single AND operator and multiple OR operators

I wanted to select a record_id with a user_id of 1 and category_id can be 1, 2, or 3. Every SELECT statement should return 1 record. View my sample table here: http://i49.tinypic.com/2ezjtk8.png How ...
3
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3answers
9k views

Return int value from boolean field in SQL select

Is there a way to return an int value for a boolean field in a sql select statement?
3
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1answer
27 views

Extra “count” row with total of 0

Consider the following: db=> SELECT ga, count(ga) FROM gb GROUP BY ga ORDER BY ga ; which gives the following output: ga | count ---+------ ? | 200 A | 100 B | 50 | 0 (4 rows) ...
3
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3answers
826 views

Is there a way, in a single SQL statement to ensure that all items in a list are present in some column?

What I'm looking for is a way of verifying that all of a list of items (let's say 'FOO', 'BAR' and 'BAZ') are all in a given table.column. This would be something like SELECT something FROM sometable ...
3
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3answers
2k 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 ...
3
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2answers
192 views

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 ...
3
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2answers
873 views

Select total number of records from common table expression

We are using common table expressions to temporarily save the search results. WITH Results ( ------ ) AS ( select --- ) SELECT * FROM ...
3
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2answers
5k views

SQL Xml returning empty root tag on empty record set

I am working on xml explicit to generate user defined nodes in xml output using Sql Server 2005 Express edition. The below code works fine, just that i couldn't manage to generate a empty node when ...
3
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2answers
11k views

Index for date column for range query in Oracle?

We have a lot: select count(*) from TBL where XDATE between ? and ? and FLD = ?; We expect to boost performance by tuning index on XDATE column (which have DATE type). What type of indexes more ...
3
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2answers
34k 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 ...
3
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1answer
39 views

Update columns values using select from external database and table in MariaDB trigger

I have two databases pdone and veevan. pdone is a kind of master and veevan keep on continue sync against an external sources. I need to perform a internal sync between veevan and pdone so I am using ...
3
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1answer
186 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 ...
3
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2answers
310 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 ...
3
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1answer
2k views

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 ...
3
votes
1answer
121 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 ...
3
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1answer
812 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 | ...
3
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2answers
7k views

How to GROUP_CONCAT DISTINCT values in a MySQL query that gets number of records and min/max values?

I'm running MySQL 5.0.88 (Coldfusion8) I have a product search which I'm querying number-of-results as well as min/max prices/rebates across the product table. I also want to include a string of ...
3
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1answer
88 views

How is encoding done in SQL database tables for pattern matching?

Are strings in table columns represented as bit patterns or Unicode? Does the database engine bring them into memory in a different representation character set from the disk-persisted ...
3
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3answers
115 views

How does like query work with indexed table

I am working in Spring-java and mysql. I have to query the table of size 100k records. Table has say 10 columns. And In my sql select query I have to make like queries with %text% search on say 4 ...
3
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1answer
316 views

Combine - Select Into, with Insert Into Select

I've read many explainations like this one here that say "Select Into ..." is to create new tables and "Insert Into ..." is to append to existing tables. I'm automating a coworker's sql scripts. ...
3
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1answer
7k views

how to fetch different data on compare rows of two tables

I have two tables in my database, one is user_app table in which user info are stored, table are as: +--------------+--------------+------+-----+-------------------+-----------------------------+ | ...
3
votes
2answers
580 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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5answers
340 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 ...
2
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3answers
1k views

How to query efficiently from Postgres to select special words?

Let's say that I have a table called words with very many records. Columns are id and name. In the words table I have for example: 'systematic', 'سلام','gear','synthesis','mysterious', etc. NB: ...
2
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3answers
289 views

Using expressions in the SELECT list to thin down a CASE statement

I have a query I'm working through rewriting - it has a huge bunch of case statements in the select list that all basically look like this: select Column1 = case when (Something = 2) and ...
2
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3answers
82 views

Platform independent select ordered by primary key

Is there a reasonably standard way to perform a select on a single table and have the result set ordered by primary key without having to specify the primary key condition explicitly? Ideally I wish ...
2
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1answer
11k 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 ...
2
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1answer
2k views

SQL Select WHERE row updated

USE [RF_WORLD] GO /****** Object: Trigger [dbo].[lastdeathtrigg] Script Date: 08/20/2012 10:52:58 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO -- ...
2
votes
1answer
653 views

How to avoid duplicating information in a series of nested SELECT statements?

I'm working on an SQL query that puts together customer history based on past purchases (the industry is venue ticketing). The report will be LARGE, something like 80-90 columns, with one column per ...
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2answers
1k views

Is there a benefit/drawback to adding LIMIT 0,1 when performing SELECT on unique key field?

I am using a MySQL database and perform many select like these: SELECT MyField FROM MyTable WHERE MyKey = 'some_value'; The purpose is to retrieve a field a value if the corresponding row exists. ...
2
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2answers
685 views

MySQL - How to check whether all values of a given SELECTed row are equals? [closed]

Using MySQL, how can i SELECT all rows whose values are equals ? For instance, suppose a SELECT of a given table as follows COLUMN_A COLUMN_B COLUMN_C ... COLUMN_N 1 2 4 ...
2
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3answers
766 views

How to speed up a multiple select query

EDIT - Putting my whole stored procedure: I have the below stored procedure: CREATE PROCEDURE [dbo].[data_Update] @Owner NVARCHAR(255), @ID VARCHAR(255), @Division VARCHAR(255), @Manager ...
2
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2answers
1k views

Select rows with repeat data within certain timeframe

As a follow-up question to my previous question on difficult row categorisation, I have another problem which I'm sure will be easily solvable. After this I plan on reading a good book or two on ...
2
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2answers
1k views

How expensive are SELECT FROM LIKE statements from a design perspective?

I have a situation running out of control regarding an ever increasing number of small static files I need to access randomly in a large directory structure. I MUST reduce the number of those files ...
2
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3answers
69 views

Generate a list from columns that do not contain a zero for each row

I have a table TAB1 in an Oracle database: +----+----+----+----+----+----+ | ID | C1 | C2 | C3 | C4 | C5 | +----+----+----+----+----+----+ | 1 | 1 | 0 | 3 | 0 | 5 | | 2 | 11 | 22 | 0 | 44 | ...
2
votes
1answer
406 views

Difference data between adjacent rows

I have a table (called Visits) with ReqTime DATETIME NOT NULL column AND Duration INT UNSIGNED column. Duration should be set to the difference of ReqTime for two adjacent rows. But Duration is not ...
2
votes
4answers
3k views

Null Or Multiple Parameters When Querying

I have a stored procedure that has a parameter that must take a comma delimited varchar list of values that can be turned into a table of values or can be NULL, such as @Values VARCHAR(10) = NULL ...
2
votes
2answers
2k views

Optimized query to fetch a record from 10 million entries

A table has 2 fields | UniqueKey | TimeStamp | ------------------------- | xfsddddq | 1024125412 | | xfstttdx | 1024125413 |< | xfsdxxau | 1024125415 | Estimated, there are 10 million ...
2
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1answer
2k 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, ...
2
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2answers
71 views

Are these extra Index fields needed?

I've designed a table as below for users who register a quiz: CREATE TABLE `registered_quiz` ( `rq_id` smallint(5) unsigned NOT NULL AUTO_INCREMENT, `user_id` smallint(5) unsigned NOT NULL, ...
2
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2answers
333 views

How do redundant indexes impact query performance?

The indexes are affecting the ADD/UPDATE operations however I was wondering whether the redundant indexes will affect the SELECT query performance or not? How the redundant indexes are handled by ...
2
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1answer
212 views

Query table A for any rows that are like any search term in table B

I need some help writing a select statement (I still don't think in sets!). Here's the scenario: I have table A with column "Name varchar(20)". I have table B with column "SearchTerm varchar(20)". I ...
2
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1answer
5k views

MySQL query to evaluate ranges in date and time elements of a datetime column separately

TABLE EventID, EventTime (DATETIME) 1 2013-09-29 23:55:00.0 2 2013-10-01 00:05:00.0 3 2013-09-29 23:55:00.0 4 2013-09-29 23:45:00.0 5 2013-10-02 23:05:00.0 6 ...