Structured Query Language (SQL). For questions about the language, not Microsoft SQL Server (tag sql-server).

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12
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2answers
3k views

Is there an execution difference between a JOIN condition and a WHERE condition?

Is there a performance difference between these two example queries? Query 1: select count(*) from table1 a join table2 b on b.key_col=a.key_col where b.tag = 'Y' Query 2; select ...
3
votes
2answers
7k views

Database design for an E-commerce website

I am new to database design. I am designing a database for an E-commerce website, there are a lot of products to be updated, but while designing for product specification table I do not understand ...
1
vote
4answers
569 views

Mysql - How to Optimize Retrieval Time in a Table

I have query which has 200 million Records in a single table. I am using BTree indexes in my table: mysql> select COUNT(DISTINCT id) from [tablename] where [columname] >=3; ...
6
votes
3answers
16k views

How to model inheritance of two tables mysql

I have some tables where I store data and depending on the type of person (worker,civil) that did a job I want to store it a table 'event', now these guys rescue an animal (thereis a table animal). ...
1
vote
1answer
324 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 ...
2
votes
4answers
11k views

Search every column in every table in Sybase Database

I'm been taxed with the task of creating an application that pulls data from our Micros Point of Sales system. The POS is using a Sybase database running on one of our servers. The database schema is ...
6
votes
1answer
855 views

Does large table variables fill up logs in tempdb?

I'm running into an issue with a DBA who claims that table variables reside in ldf of the tempdb and when large amount of data is loaded into the table variable, the tempdb's logs fill up. The DBA's ...
4
votes
1answer
86 views

Covering Index Question

I have the following query Select Pt.PRODID, PT.INVENTREFID, Inv.ItemName, PT.ItemID, Configid, Pt.QTYSCHED, PT.DLVDATE, Pt.CREATEDDATETIME, pt.SCHEDEND, CASE Left(PT.INVENTREFID, 3) WHEN ...
2
votes
2answers
257 views

Is this relation in 3NF?

I created a relation called Customer and defined as: I just wanted to know if it is in 3NF? My concern is regarding address, since customer may have the same address.
2
votes
2answers
393 views

SQL Max() revision number

This SQL returns a table with everything unique, which is what I want. However, if there are two (or more) event numbers, I need it to return the line with the highest rev_num for that eventnum. I ...
1
vote
2answers
130 views

Does this query make sense?

I recently migrated a database from Sybase ASE to Microsoft SQL 2008r2. One category of queries that was broken in transit is: SELECT person_id FROM leaveperiods WHERE group_id=146 GROUP BY ...
2
votes
1answer
108 views

What is the equivalent of a “Certificate of Destruction” when using a cloud-hosted database?

We have a Rails application hosted by Heroku and using an Heroku Postgres database. Some of the information we store is considered to be sensitive by our users, and we've been asked if we can provide ...
4
votes
3answers
739 views

Backup strategies for zero data loss

I am working on one project and it has around 100K records. We can afford a downtime of 1 day but we need the data to be always available to us in latest state. I've gone through two options: 1) ...
0
votes
2answers
463 views

Large time difference between two almost identical simple queries…why?

I'm trying to understand why is there so much difference in execution time and CPU usage between two simple queries that only differ in a computation. The queries are the following: SELECT ...
1
vote
2answers
5k views

How to find DELETE and UPDATE statements that have been executed on a database?

I am trying to find out what delete and update statements have been executed on a certain database in a certain period of time. I came across this following query, but it generates an error message: ...
0
votes
1answer
239 views

What is the maximum number of rows in a clustered index on datetime column?

I would like know what the max no of rows is in a clustered index (non-unique) on a datetime column table in SQL Server 2008R2.
0
votes
2answers
553 views

Using MySQL InnoDB as an Archive

My site has a main MySQL InnoDB table that it does most of its work on. New rows get inserted at a rate of 1 million per week, and rows older than a week gets moved over to an archive table on a daily ...
2
votes
2answers
815 views

Check if row exists

I need to write a query that will insert a row only once, even if the query is run multiple times. Being new to SQL (well new-ish), I did an if not exists(...) but a friend said he preferred deleting ...
0
votes
3answers
233 views

Select MaxDate where hh:mm:ss makes the difference

How to select the maximum date from a table where hh:mm:ss is selected? My query is the following, and returns the latest date, but if there are different times recorded, the date will be returned ...
6
votes
2answers
5k views

SQL Server alter table to change TEXT to NVARCHAR(MAX) greatly increasing database size

I need to update a SQL Server database thats about 18GB in size to change a significant number of TEXT columns to NVARCHAR(MAX). The problem I'm having is after executing all the alter table ...
3
votes
1answer
330 views

Creative workaround for granting edit rights to individual jobs for a group?

We have two developers that say they can not function without full rights to a few jobs on our database server. They both want rights to the same jobs. Given that it seems that MS doesn't seem to be ...
4
votes
1answer
3k views

Join To a @Table Variable is running ineficiently

Alright so I have a report sproc that was running incredibly slow. Customers were complaining that the report would not run so I started investigating exactly where in the sproc the problem was and I ...
1
vote
2answers
6k 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 ...
0
votes
3answers
986 views

Fixing a query that returns failed job information

I' using a SQL Server 2008 Sp3 environment. I have a query that returns information about failed jobs from the last 10 minutes. If a job has two schedulers (for example - a job that runs every 10 ...
2
votes
2answers
5k views

MySQL Replication without stopping master

I am currently setting up a replication for my database one of the ways i am thinking of synchronizing the master and slave without write locking the master, is by first taking a log position then ...
5
votes
1answer
2k views

How to improve performance on PostgreSQL when using multiple concurrent processes?

Seeing query performance which is not satisfactory on our Python application, which runs several processes that use SQLAlchemy core to access a PostgreSQL 9.2 database. We may have around 100 - 200 ...
1
vote
1answer
906 views

Question about Oracle's interpretation of “host cpu utilization” in v$sysmetric view

I am studying the v$sysmetric view from Oracle and trying to understand what is Oracle's interpretation of "Host CPU Utilization" It says in the metric_unit as % busy/(idle + busy), but what is busy? ...
1
vote
0answers
705 views

Efficiently retrieve big amount of data based on date range

Table EVENTS TimeStamp |O.Name |Location |Source | 2008-11-12 |Pretorian|Európe |England | 2009-12-24 |Lex Rosa |Európe |Italy | 2010-01-01 |Nasdaq |USA |Whasington | ...
2
votes
2answers
3k views

Only one NULL for one part of primary key

I have two date columns : "start date" and "finish date". I want to make sure that there can be only one null value in the "finish date" column (which should be current state if it's NULL) for one ...
0
votes
1answer
136 views

Implementation of stack in MySQL

I had an abstract idea of implementing a stack in MySQL. Tried a lot of Google work but couldn't reach to any logical conclusion. The Stack must be a collection of tables with the stack top pointing ...
4
votes
1answer
29k views

What queries is Oracle executing, how frequently, and time-taken?

I have a (Java) web-application, that of course executes many queries (selects, inserts, updates, deletes) to the Oracle Database. I want to find out the following for last 7 days: SQLQuery ...
1
vote
2answers
63 views

Need logic to collate data

I have a table in the below structure. phone bigint answer_time datetime I should group all phone numbers, and its total number of attempts and mention its no:of time answered and no:of time not ...
0
votes
0answers
426 views

Error in creating trigger in phpMyAdmin

I have 4 tables: event: event_id(p.k) | uid | circle_id(f.k) activity: uid | performed_activity_id(f.k->event_id) | activity_type_id follow: follower_id | circle_id(f.k) notification: sender_id ...
1
vote
1answer
69 views

Hard Parse on Non-Identical Statements?

Let's say I have this query : SELECT X FROM Y If I run it for the first time then it would do a hard parse. After that, I run this query : select x from y With just a difference in alphabetical ...
2
votes
1answer
6k views

The Cluster service failed to bring clustered service or application 'SQL Server (MSSQLSERVER)' completely online or offline

SQL Server service restarted/stopped, which cause the production database down n find this errors in System log. ERROR5:The Cluster service failed to bring clustered service or application 'SQL ...
1
vote
1answer
550 views

mysql query - how to delete duplicates based on highest int?

I'm running a reverse auction website and I need to delete the duplicate bids and keep only the highest amount . lastPriceBid_rounded is the "amount". The duplicate is defined by the userId. ...
7
votes
2answers
2k views

Different results rebuilding an index online and offline

I have a non-clustered, non-unique index on a foreign key column of type bigint. When I rebuild the index online, the average fragmentation drops to 3%, with 2 fragments, and 30 pages. When I run ...
9
votes
4answers
834 views

Is a join optimized to a where clause at runtime?

When I write a query like this... select * from table1 t1 join table2 t2 on t1.id = t2.id Does the SQL optimizer, not sure if that is the correct term, translate that to... select * from table1 ...
4
votes
1answer
87 views

Index Evaluation

I have been doing some index evalaution on a table and this is the first time I have ever looked at how well indexes are performing so and would like some advice on a certain index. The non ...
3
votes
1answer
4k views

Select the top 5 records and the specific column from each table in the same database

I have 50+ tables in a database. I don't want to use the following SQL on each table in a database. select top 10 * from {table_name} So, is it possible to display the first 10 records PLUS only ...
2
votes
3answers
8k views

How to select the first 10 records for each table in the same database using sql

I have 50+ tables in a database. I don't want to use the following SQL on each table in a database. select * from {table_name} So, is it possible to display the first 10 records for each table ...
3
votes
2answers
2k views

What is the difference between using varchar(100) and varchar(255)?

I want to know difference between varchar(100) and varchar(255) in terms of memory usage and programming problems of using more memory.
1
vote
2answers
233 views

Suggestion for storing a lot of simple data

I'm looking to crawl a lot of webpages (500,000,000,000) records and be able to store the linking structure for a later date. The way I planned on laying out the database was as follows: 2 Tables ...
3
votes
1answer
68 views

Special ordering

I have a hierarchical query but I don't manage to order it as I want. I have a column named sequence that indicates how to order it but the data is kinda mixed up and I cant do it properly. This a ...
7
votes
2answers
1k views

Is there any difference between putting a column alias at the start or the end of the column definition?

I've always seen and written my column aliases as SELECT 1 as ColumnName but today came across a query that used SELECT ColumnName = 1 Is there any difference in how these two queries get ...
0
votes
1answer
519 views

Connecting to an SQL Azure Database from SSMS - IP Restriction

I am trying to connect to a new SQL Azure Database via SQL Server Management Studio. The client box running SSMS is hosted on a production DB so we restrict access on 1433 to just a handful of IPs ...
5
votes
3answers
162 views

Filtering data that could have more than one category

I have a table like the following: Annotation ( document, term, category ) Where document and term are some ID, while category is an integer. The couple document - term is not unique, ...
3
votes
2answers
1k views

Problem with order by in MySQL subquery

I'm running a query that runs in about 2 seconds when the subquery does not include the order by date_sold clause. However, when I add the order by clause, the query runs forever. I'm confused, since ...
0
votes
2answers
94 views

How to organize a single query to several sql servers?

I need to make an inner join sql query to several SQL Servers (one is 2000 and another is 2008 R2). The query is like the following: SELECT k.ID, k.NAME, k.BIRTH, l.PROFILEID FROM ...
0
votes
1answer
76 views

Faster joining on 'most recent' related rows

I have a bug tracking application. The bug table stores very little, because every state change to a bug happens by adding a comment. For example, the current state of a bug is determined by the state ...