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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Determine last time a mysql table was accessed (i.e. SELECT'ed)

In my mysql DB schema there are old tables that are no longer used. I want to come up with a systematic way to show my developer a list of tables and last time they were read (SELECT'ed, not ...
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40 views

Should I drop this column or is there a query that can achieve a results table without duplicate columns?

I use a column named active in several of my database tables to adjust whether a particular entry/row/user/etc should be included in future query result tables instead of deleting the information. ...
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163 views

Running queries directly on DB2 databases

Just have a general query, if it is really fine or safe to run long select queries on RDBMS production Databases specifically DB2? If NO, what are the major risks and issues in executing select ...
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625 views

How do I query for leaf nodes in a hierarchy using a closure table?

I have some hierarchical data (representing musical instruments and playing techniques), where each leaf in the hierarchy is an audio file. The nesting depth of leaf nodes will vary because some ...
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263 views

Slow running query with inner SELECT in where clause

I have a query that looks like the following: USE DATABASE3; GO SELECT t1.COL1 AS COLUMN1, t2.COL2 AS COLUMN2, t1.COL3, t1.COL4 AS COLUMN4, t1.COL5 AS COLUMN5, ...
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208 views

INSERT INTO selected columns creates new column from JOIN [closed]

I have an INSERT INTO ... SELECT.. query that uses a JOIN on two tables. The results of the query should take a subset of the information and insert it into an existing table. That part works, but the ...
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4k views

Selecting multiple columns from multiple rows in one column (subquery?)

I'm working with MySQL 5.1.68. I have a situation where I'd like to select rows from another table into a column. I'd like to output this: id # name # citizen_name (multiple citizen names) 1 # ...
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2k views

How to run a SELECT query within while loop in PHP?

Within a SELECT query via PHP while loop, I need to run a mysql SELECT query as $result1 = $mysqli->query("SELECT * FROM table1"); while ( $row = $result->fetch_assoc() ) { if ( $row['X'] == ...
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351 views

Select records that do not have associations outside a certain list

I have a mySQL table of nodes and each node can be associated with many categories. I have a list of category ids that are acceptable (498, 499). I want to select only nodes who do not have ...
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162 views

I would like to query a range of criteria on multiple columns in MySQL

I have 3 columns in a mysql table. I'm using Innodb engine. I want to be able to search for some values on those columns and also anything close to those values. For example : We have 3 columns as ...
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305 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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2k views

How do I perform a UNION query on a dynamic list of tables?

My database has an unknown amount of tables, named with the same prefix followed by a random string: _ct_<random_string>. Each of these tables has the same data structure. I also have another ...
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72 views

How can I query to do this?

I have 2 tables, in feeds I have my feeds and (feeds.ID) is the primary key. second table is items. and feeds.ID is realted to items.feed_ID, so with a simple inner join i can extract the data of each ...
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265 views

Shift db data to another column

I have the following table id | ev_id | ev_loc_id | a | b | prev_a | prev_b If I the (ev_id AND ev_loc_id) not exist in the table then I just insert them, otherwise I'm putting ...
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22 views

two column compare ,get count(*) of two column A value same cloumn B value

I have a Mysql table as --------------------- -- page - user -- --------------------- -- page a - user 1 -- -- page a - user 2 -- -- page a - user 3 -- -- page b - user 1 -- -- page b - user 3 -- ...
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46 views

Slow Query with LIMIT

We have this query: SELECT "messages".* FROM "messages" WHERE "messages"."account_id" = 1 AND "messages"."status" = 'unread' AND (created_at >= '2014-04-24 01:00:00.000000') ORDER BY id DESC It ...
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29 views

Select all foreign key relationship chains from any set of potentially gapped table names

I am using this query to find all foreign key relationships: SELECT con.relname AS child_table, att2.attname AS child_column, cl.relname AS parent_table, att.attname AS parent_column ...
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37 views

use variable to determine the name of a column in the select in postgre

I'm trying create a update for a new structure of tables from a old table, but not using functions. I'm trying create a script to it. The old table is like this: -- old table (OldTable) name| col_a | ...
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40 views

Selecting most recent date when dates are stored in another table

Working in a MySQL database, I have tables set up like this: Table song_instances has song_id (int), meeting_instance_id (int) The meeting_instances table has columns meeting_instance_id (int), ...
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36 views

Mysql: Problem using GREATEST with IFNULL and join

I have a query selecting the greatest value of 2 timestamp. To Achieve it I'm calling: SELECT GREATEST( IFNULL( tableb.create_time, 0 ) , IFNULL( tablea.create_time, 0 ) ) I'm using IFNULL because ...
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37 views

Multiple selects ordering desc from single table

I'm trying to do multiple selects to give multiple ordered columns. I'm struggling to get the below mysql query to achieve the output I want. SQLfiddle: http://www.sqlfiddle.com/#!2/a1002/3 ...
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SELECT, PROJECT, CARTESIAN PRODUCT and JOIN

I have the following tables; DOG +----------------------------------------------+ | Name Type Age Kennel_name Owner_name | +----------------------------------------------+ ...
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95 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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49 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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78 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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408 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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175 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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42 views

MAX (id) function with MySQli

How can I use the following statement to return only the record with the maximum PersonID from the table? /* Create the prepared statement */ if ($stmt = $mysqli->prepare("SELECT Max(PersonID) AS ...
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3answers
489 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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1answer
43 views

Work with table named Group [closed]

I have a table named Group in my database , when I try to work on it it gave error : SELECT GroupID,GroupName FROM Group it said : Msg 102, Level 15, State 1, Line 1 Incorrect syntax ...
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2k 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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669 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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37 views

Select into existing table where ID is in another table [closed]

I have one table containing ~35k IDs (TableC), one table that features multiple columns (TableA), amongst others the ID from the before mentioned table and a third empty table, featuring the same ...
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3answers
113 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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2k 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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591 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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2answers
191 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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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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32 views

How to use relationships to extract data via select

Disclaimer: Novice in SQL I have 3 tables. There is one "major" table (labeled used_for_lookup below) used to do look-ups on and the other two (labeled fid_table and did_table below) are foreign keys ...
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37 views

Using count() and sum() in a calculation in a select

I am trying to do the following in a single select. We have a SAAS that has Company records and User records. A User is a member of a Company (Company.CompanyId = User.CompanyId). In the User record ...
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1answer
30 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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79 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
80 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
102 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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3answers
123 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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3k 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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504 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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70 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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2k 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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35 views

Move/Copy unique entries only from TableA to TableB, if it's not in the destination table

I'm required to move every unique entry from TableA to TableB, it the unique entry from TableA is not already in TableB. Both tables look the same, they don't have any keys, but the combination of to ...