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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`Select` query take more time than it should

I have a MySQL database table with nearly 23 million records. This table has no primary key, because nothing is unique. It has 2 columns, both are indexed. Below is its structure Below is some of ...
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57 views

SELECT, PROJECT, CARTESIAN PRODUCT and JOIN

I have the following tables; DOG +----------------------------------------------+ | Name Type Age Kennel_name Owner_name | +----------------------------------------------+ ...
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70 views

How to join the tables in mysql to get wall messages and comments with name of person ? Only user and his friends messages

I have four tables in my mysql database as shown in the image url provided. I want to select data from the tables without duplication. I want to show messages and comments on wall according to the ...
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1answer
33 views

SELECT showing two COUNTs

I had this table: tblA id | name | value 1 nameA 1 2 nameA 0 3 nameB 0 4 nameC 0 5 nameC 1 6 nameC 1 As you see, Value can be 1 or 0 I need to perform a query ...
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1answer
76 views

Mysql with index [closed]

I have this following sentence: SELECT Day(C.DataCadastro) AS Dia, Month(C.DataCadastro) AS Mes, Year(C.DataCadastro) AS Ano, COUNT(I.Plano) AS Total FROM clientes AS C ...
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1answer
370 views

Merge 2 tables and fetch data one by one

I have two tables: product & offers. products has (prod_id, category_id, prod_name, brand, price, status) offers has (offer_id, prod_id, offer_type, discount_amt, validity) I want to display ...
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162 views

Get all comment.message, status.message, users.* and profiles.* where users.user_id exists in friend.friend_id or friend.user_id

I need some help building this query because it's a bit complicated at least for me. I need to get all comment.message, status.message, users.* and profiles.* where users.user_id exists in ...
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3answers
458 views

Can a RDBMS connect to a remote server, execute a select query and copy them into a local table just with SQL commands?

I'm sorry it may sound stupid but I've been wondering about how multiple databases are automated before the virtualization era. Can a DB Adminsitrator make a stored procedure to get data from a remote ...
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599 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
354 views

Postgres: How to insert row with autoincrement id

There is a Table "context". There is an autoincrement id "context_id". I am using sequence to retrieve the next value. SELECT nextval('context_context_id_seq') The result is: 1, 2, 3,...20.... But ...
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3answers
80 views

How to create an Access query to find # symbol into a field?

It seems easy but I'm missing something. I have a MySQL database that is connected from access through ODBC connector. I'm looking for the fields where there are # symbol but I'm getting zero ...
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177 views

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
81 views

Can you search using an index while indexes are being updated in oracle11g?

I am using oracle 11g. I noticed some performance problems that causes hanging on some search operations. Can I still search based on an index while that index is being updated in the database?
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1answer
17 views

PostgreSQL SQL syntax - JOIN and substrings

I have a single table of hostnames and NFS exports, some but not all of which are related. Example entries: HOST VOLUME ----- ---------- host1 vol1 host1 vol2 host1 ...
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1answer
67 views

ORDER BY that doesn't contain repeating values

Relevant SQL Fiddle (postgres 9.2) How do I state a SELECT .. ORDER BY .. that avoids having repeated values for a column? That is, for rows of the column "rank" (1,3,3,1) how do I get a result so ...
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3answers
57 views

New field based on sum field

I'm trying to create a new field based in another (sum field) SELECT sum(price) AS old_price, old_price+100 AS total_price FROM sales This returns Unknown column 'old_price' in 'field list' sum ...
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1answer
100 views

performance difference between < and <=

I remember that there is a performance issue with SQLs that use "<" against "<=" because of statistics and/or histograms and/or the data itself, but I dont remember exactly the issue. I know ...
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120 views

How to query for 'First showed up as'

Given the following table: Date Trd (INT(10)) Code (VARCHAR(10)) T-Date 1-Jan-14 1 B 1-Nov-13 1-Jan-14 2 B 3-Oct-13 ...
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2k views

How to select only first column dynamically on mysql

I have to select only first column. Because of i dont want to select all columns like SELECT * FROM table. But my first columns may vary like following: id article_id user_id product_id page_id etc.. ...
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355 views

SQL output formatting

I want this: "ACCOUNT_ID","MAJOR_VERSION","MINOR_VERSION","COUNTRY","ACCEPTANCE_TIMESTAMP","AGREEMENT_ID" "abcdefgh-1234-5678-ijkl-mnopqrstuvwx","20110901","1","CN","1329574013737","tos" But I get ...
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2answers
66 views

Difference between the given queries

I am required to retrieve the list of pno ( product_id ) for the products which were purchased by two customers. For this, I have been given two relations which are ( along with the attributes ) as ...
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1answer
1k views

How to create an Sql table from SELECT with a multiple row DISTINCT constraint?

I want to create a table from a SELECT statement based on a multiple row DISTINCT, but PostgreSQL does not allow me to do it. I need to create a table where the elements were previously selected from ...
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1answer
462 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

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
24 views

Is there any performance difference between a group by statement and nested select statements in sql?

I am curious to know about the differences between using group by statement and nested selects to achieve the same result. for example consider I have two tables such as the following: tblPurchase ...
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1answer
29 views

How to sum the buy order and sell order in one row per each ticker

I have a table containing some trading information of several tickers and I would like to divide the data into sum(Amount) for buy and sell separately, grouping by each ticker. I have one table ...
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2answers
60 views

SELECT query with referenced subqueries

How does one reference the currently-grouped by field in a subquery? Consider a table with the following data: Client Status Size 1 A 500 1 B 1500 2 ...
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1answer
28 views

How to return a result set from oracle procedure ?

How can i return a result set from a stored procedure in oracle ? suppose i want to return a table from a simple select statement such as this : Select * from tblTest I tried this but this seems ...
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90 views

Multiple SELECT vs single SELECT over TCIP

My question is a performance one: I need to select roughly 400+ rows, i know their ids. currently i loop in code and fire off multiple queries over tcp/ip - because its easy: ... select [columns] ...
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1answer
3k views

MySQL: split value in column to get multiple rows

I have some data in a table like so: product_id categories 10 9,12 11 8 12 11,18,5 I want a select statement that would produce this output: product_id ...
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1answer
75 views

Get all items from list table which don't have a successful log entry for 'sent' in log table

How might one retrieve items that when joined either don't have a specific field (sent), or if they do have that field (sent) then they have an additional field (failure_reason) as well for every sent ...
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3answers
80 views

prepared statements are not inserted

i am new to JDBC and trying following code. Could not find the error in it try{ Connection con = ConnectionProvider.getCon(); stmt=con.prepareStatement("insert into ...
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1answer
36 views

Should the value of a select max be indexed when the where clause is already indexed

I have a customer_orders table in a schema designed to be shared between multiple companies. Each customer_order has an invoice number that should always start at 1 and increment based on company ...
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433 views

How to use OR in query with priority?

In a simple query like SELECT * FROM table WHERE id='x' OR id='y' How to give a priority to get only one of the WHERE clauses? I mean getting rows with id='x'. Only if there is no row, get row ...
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1answer
147 views

Conditionally limit MySQL SELECT query

My goal is to select rows from a mysql table, but according to certain column. Normal SELECT would be: SELECT ti.id, ti.userid, ti.date, ti.duedate, ti.datepaid, ti.subtotal, ...
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1answer
149 views

Order of where clause evaluation

If I have a MySQL table which has content from the last 3 months I actually do the following: SELECT SQL_BUFFER_RESULT SQL_CACHE count(id) cnt FROM `mDelivered` where _campaign = 2 and `session` = ...
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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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2answers
689 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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668 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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96 views

SQL and Multiple Indexes

Consider the following table: i | a | b | c -------------- 0 | 1 | 2 | 3 1 | 4 | 5 | 6 2 | 7 | 8 | 9 3 | x | y | z The table, in the end, will have several thousand rows, and even more columns then ...
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3answers
184 views

How can I select data and the total to cursors?

I have a table like this: ID | Name ------------ 1 | AA 2 | AA 3 | AA 4 | BB I want to select all rows where Name like 'AA' in a cursor and get the count from this result in another ...
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1answer
29 views

What's the difference between INSERT … SELECT and SELECT INTO

Let's say I have a table item and an other one versionned_item. From time to time, I want to copy data from item to versionned_item. What I did is WITH subset AS (SELECT ...) INSERT INTO ...
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44 views

SQL insert into … values (…, select(…))

I am trying to insert 25 users, user1...25 into Members with the same GR_ID = 2 with command: insert into MEMBERS (GR_id, username) values (2, (select username from USERS where username like ...
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1answer
22 views

Get the most present elements from many fields

Here is my table: id|item0|item1|item2 --+-----+-----+----- 1 | 10 | 12 | 12 2 | 12 | 68 | 13 3 | 15  | 13 | 10 I just want to get the most present number of all itemX columns. The query ...
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1answer
29 views

How do I select the value with SERIAL data type in postgres

I wanna ask how to select coloum that has SERIAL data type. I already try to do that but the output is like this 'Resource id #3', and not just '3' I use SERIAL so I dont have to input ID like when ...
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1answer
30 views

Selecting 3MB (or more/less) data from database server

I installed PostgreSQL Server on my Windows 7 machine. I created database and a simple table, and populated the table. Now I want to connect through the network with my Postgres server and select a ...
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1answer
34 views

MySQL locking tables / rows on select statement

I have a web app that does an addition to a field based on a user input. So say for example User-A inputs 7, my web app would first query the contents of the field for the current number in there, ...
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1answer
58 views

Low-level relational operators from SQL

I have been asked to outline the sequence of commands using low-level operators (join/project/select) that are used in the following SQL statement; SELECT d.name, k.city FROM DOG d, KENNEL k WHERE ...
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60 views

how to correctly return values from a function

I would like to create a function that queries a user table by passing a username and a password, the function is supposed to return 'Y' if the username / password are correct and 'N' if they're not. ...
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1answer
42 views

Design for hierarchical embedded database

The goal is to construct a hierarchical database of Objects having the following format: TypeA -> ObjectA [values, contains ObjectB*, ObjectC*, etc.] TypeB -> ObjectB [values, contains ...