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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How to only update if nothing has changed? I need to validate several things before I insert

Say I have two tables: runners and waypoint_checkins. I want to add waypoint checkin entries but I can never add a waypoint if the runner has finished the race, (see below for schema). Finally. A ...
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2answers
381 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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2answers
6k 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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Select only those records that have different/multiple values for a particular column

Below is an example of my membership table. There some records having multiple values in the email field. I only want to select those records that have multiple email values: Member table ID ...
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1answer
1k 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 | '...
4
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1answer
187 views

Fast alternative for “NOT IN”

I have a table A that got a field called id that is the primary key of this table. I also have a table called B which also have a field called id as primary key. Now I want to get all rows from ...
4
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186 views

Mysql: Problem using GREATEST with IFNULL and join

I have a query selecting the greatest value of 2 timestamps. To achieve it I'm calling: SELECT GREATEST( IFNULL( tableb.create_time, 0 ) , IFNULL( tablea.create_time, 0 ) ) I'm using IFNULL ...
4
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161 views

how to cache a subset for cascading select queries in mysql

Here is another database problem I stumbled upon. I have a date-range partitioned MyIsam look-up table with 200M records and ~150 columns. On this Table I need to perform cascading SELECT-Statements ...
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887 views

SQL Server Deadlock - Two SELECT Exclusive Locks on Exact Same Index and Key [closed]

How is the deadlock graph below possible? How did two SELECT statements simultaneously acquire an exclusive lock on the exact same resource? The exclusive locks were on the primary key index for ...
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1k views

Single query to return counts over different IDs in a single record

select count(title_id)as algodata from titles where pub_id =1389 select count(title_id)as binnet from titles where pub_id =0877 select count(title_id)as newmoon from titles where pub_id =0736 ...
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2answers
3k views

Does the SELECT statement count into DML?

Looking at the name Data Manipulation Language (DML) I would assume, that all contained statements are actually for manipulating data. As far as I know the SELECT statement can only be used to query ...
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269 views

Listing rows with a WHERE condition

I am struggling with a SQL query that lists hosts that are offline. Problem The problem occurs when I need to list hosts that don't have any ports open (status = 0), so looking at the table at the ...
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9k 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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4k 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 ...
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3answers
175 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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3k views

Select query according to date

We have a table to store the Events. Table has got a schema like EventID INT Primary Key EventName NVARCHAR(100) StartDate Datetime EndDate Datetime So in the front end we want to show the events ...
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Does the MySQL primary key affect the efficiency of a SELECT query?

Does the primary key serve any purposes apart from uniquely identifying a specific row? For example, a table with an autoincremented primary INT key could greatly aid in search due to the option of ...
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1answer
5k 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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507 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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1answer
320 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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13k 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?
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2answers
83 views

Inserting rows with WHERE condition

Structure 1 table named: scan 2 columns named: id, and date Problem I have two working queries, a SELECT and then an INSERT which I would like to merge together creating a INSERT where the ...
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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 ...
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1k 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 ...
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1answer
3k 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
789 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 ...
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47 views

Why am I getting ORA-00937 error using only aggregate functions?

Here is a sample of what I'm trying to do: SELECT COUNT(T1.FIELD) + ( SELECT COUNT(T2.FIELD) FROM TABLE2 T2 ) FROM TABLE1 T1 I don't see a need for group by clause in ...
3
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1answer
109 views

Sorting Order by GETSORTED

In my sybase 12, when I look at the showplan of a select distinct query, I see GETSORTED in the showplan's output. I've searched through the entire internet (YES!) and I can not seem to find a link ...
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1answer
45 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) ...
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2answers
18k 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 ...
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3answers
3k 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
195 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 ...
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1k 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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55 views

Self-JOIN with occurrence count

I use PostgreSQL 9.4 and I have a table called certificates containing the following columns: CREATE TABLE certificates ( id serial PRIMARY KEY, common_name varchar(255) NOT NULL, state ...
3
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2answers
344 views

Query parent table and get child tables columns

I have two tables, one inherits the other: CREATE TABLE parent ( col1 INTEGER ); CREATE TABLE child ( col2 INTEGER ) INHERITS( parent ); // Insert some data INSERT INTO parent( col1 ) ...
3
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2answers
36 views

Select only rows with at least 2 non-missing values

I'm pretty new to MySQL (used to programming in R/Stata), and getting stuck on this - I'm probably going about it the wrong way. Any pointers would be appreciated! I have a large database (a couple ...
3
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2answers
30 views

Howto (async?) preview intermediate resultset

Is it possible to retrieve parts of the resultset from SQL Server queries in advance? For instance if I run a query that will return 20,000 rows, is it possible to throw the results in packages of ...
3
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1answer
251 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
267 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 ...
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2answers
6k 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 ...
3
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1answer
3k 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
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2answers
96 views

MySQL - Order by closest value on multiple columns

I have a table for a game lobby. In this lobby a user gets put in their connection and their level. In my SQL statement I am getting all the users in the lobby which are between +5/-5 of the user's ...
3
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1answer
2k views

How can I make a select statement get blocked?

Hello I am trying to intentionally make a SQL select statement get blocked by another simple SQL delete or update statement, for the purpose of learning. I prefer only InnoDB tables. To prepare the ...
3
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1answer
187 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
3k 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 ...
3
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2answers
44 views

Get rows with minimum value

I have tables company: company_id | - - - - - - - - - - - - - - 1 | 2 | employee: employee_id | - - - - - - - - - - - - 1 ...
3
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3answers
296 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
658 views

Better way to select from nested tables in PostgreSQL

I have the following schema with millions of rows in the match table and each match have two sides (away and home). I want to create a view which shows the most significant data regarding the matches ...
3
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1answer
397 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
2k 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 (...