General MySQL Oracle SQL Server

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What Causes Index Fragmentation in SQL Server
What Causes Index Fragmentation in SQL Server? Index fragmentation is usually caused by deleting of existing rows or updating existing values of the indexed column. Inserting new rows should not cause any index fragmentation. This tutorial exercise shows you how update statements of 50000 rows on th... 2016-11-08, 3485🔥, 0💬

Creating a Large Table with Random Data for Indexes in SQL Server
How To Create a Large Table with Random Data for Index Testing in SQL Server? If you want to see how index can be used to improve data search performance, you have to build some large tables, which requires large amount of random data. This tutorial exercise helps you to build a large table with pur... 2016-11-13, 3484🔥, 0💬

Data File for MyISAM Storage Engine in MySQL
Where Table Data Is Stored by the MyISAM Storage Engine in MySQL? By default, MySQL provides \mysql\data directory for all storage engines to store table data. Under \mysql\data directory, each database will have its own subdirectory to store table data. If a new table is created with the MyISAM sto... 2017-09-01, 3483🔥, 0💬

Disk Space Needed for an Export Job in Oracle
How To Estimate Disk Space Needed for an Export Job in Oracle? If you just want to know how much disk space for the dump without actually exporting any data, you can use the ESTIMATE_ONLY=y parameter on the expdp command. The following tutorial exercise shows you how a system user wants to see the d... 2016-10-15, 3482🔥, 0💬

What Is mSQL in MySQL
What Is mSQL in MySQL? Mini SQL (mSQL) is a light weight relational database management system capable of providing rapid access to your data with very little overhead. mSQL is developed by Hughes Technologies Pty Ltd. MySQL was started from mSQL and shared the same API.   ⇒ What Is SQL in MySQL ⇐ ... 2017-07-15, 3477🔥, 0💬

Quickest Way to Export Data to a Flat File in Oracle
What Is the Quickest Way to Export a Table to a Flat File in Oracle? The quickest way to export a table to a flat file is probably to use the SQL*Plus SPOOL command. It allows you to record SELECT query result to a text file on the operating system. The following tutorial exercise shows you how cont... 2018-06-27, 3468🔥, 0💬

What Is an Initialization Parameter File in Oracle
What Is an Initialization Parameter File in Oracle? An initialization parameter file is a text file that contains a list of initialization parameters. The file should be written in the client's default character set. Sample initialization parameter files are provided on the Oracle distribution mediu... 2020-07-07, 3461🔥, 0💬

"ALTER INDEX ... REBUILD" - Defragmenting Indexes in SQL Server
How To Rebuild Indexes with ALTER INDEX ... REBUILD in SQL Server? When an index is defragmented to a large percentage, like &gt; 30%, you can use the "ALTER INDEX ... REBUILD" statement to rebuild the index. Here is a tutorial exercise on rebuilding indexes: USE FyiCenterData; GO UPDATE fyi_lin... 2016-11-08, 3459🔥, 0💬

Concatenate Two Text Values in Oracle
How To Concatenate Two Text Values in Oracle? There are two ways to concatenate two text values together: CONCAT() function. '||' operation. Here is some examples on how to use them: SELECT 'FYI' || 'Center' || '.com' FROM DUAL; FYICenter.com SELECT CONCAT('FYICenter','.com') FROM DUAL; FYICenter.co... 2019-12-02, 3456🔥, 0💬

Differences between INTERVAL YEAR TO MONTH and INTERVAL DAY TO SECOND in Oracle
What Are the Differences between INTERVAL YEAR TO MONTH and INTERVAL DAY TO SECOND in Oracle? The main differences between INTERVAL YEAR TO MONTH and INTERVAL DAY TO SECOND are: INTERVAL YEAR TO MONTH stores values as time intervals at the month level. INTERVAL DAY TO SECOND stores values as time in... 2020-04-25, 3451🔥, 0💬

ONLINE/OFFLINE - Database States in SQL Server
What are database states in SQL Server? A database is always in one specific state. For example, these states include ONLINE, OFFLINE, or SUSPECT. To verify the current state of a database, select the state_desc column in the sys.databases catalog view. The following table defines the database state... 2016-11-20, 3443🔥, 0💬

Privilege to Create Views in Oracle
What Privilege Is Needed for a User to Create Views in Oracle? To be able to create views in a user's own schema, the user needs to have the CREATE VIEW privilege, or the CREATE ANY VIEW privilege, which is more powerful, and allows the user to create views in other user's schema. The following tuto... 2019-06-29, 3441🔥, 0💬

Managing Oracle Tablespaces and Data Files
Where to find answers to frequently asked questions on Managing Oracle Tablespaces and Data Files? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Managing Oracle Tablespaces and Data Files. Clear answers are provided with tutorial exercises on cr... 2019-04-17, 3441🔥, 0💬

Variable Names Collide with Column Names in Oracle
What Happens If Variable Names Collide with Table/Column Names in Oracle? When a variable name collides with a column name, PL/SQL will use it as the variable if it is used where variable is allowed; It will be used as the column, if it is used where variable is not allowed but column is allowed. He... 2018-09-24, 3439🔥, 0💬

Setting New Values to Parts of a DATETIME Value in SQL Server
How To Set Different Parts of a DATETIME Value in SQL Server Transact-SQL? In SQL Server, you can get different parts of a DATETIME value with the DATEPART() functions. But there is no function that allows you to set different parts to a DATETIME value. For example, you a date_of_birth column as DAT... 2017-02-08, 3439🔥, 0💬

"@@FETCH_STATUS" - Looping through Result Set in SQL Server
How To Loop through the Result Set with @@FETCH_STATUS in SQL Server Transact-SQL? The FETCH statement only returns one row from the result set. If you want to return all rows, you need to put the FETCH statement in a loop. A simple way to stop the loop to check the system variable @@FETCH_STATUS, w... 2016-10-17, 3438🔥, 0💬

Delete Multiple Rows from a Table in Oracle
How To Delete Multiple Rows from a Table in Oracle? You can delete multiple rows from a table in the same way as deleting a single row, except that the WHERE clause will match multiple rows. The tutorial exercise below deletes 3 rows from the fyi_links table: SELECT * FROM fyi_links WHERE id &gt... 2020-01-04, 3432🔥, 0💬

Create a Test Table for Transaction Testing in Oracle
How To Create a Test Table for Transaction Testing in Oracle? If you want to practice DML statements, you should create a testing table as shown in the script below: &gt;cd (OracleXE home directory) &gt;.\bin\sqlplus /nolog SQL&gt; connect HR/fyicenter Connected. SQL&gt; CREATE TABLE... 2019-09-04, 3422🔥, 0💬

Define a Sub Function in Oracle
How To Define a Sub Function in Oracle? A sub function is a function defined and used inside another procedure or function. You need to define a sub function in the declaration part of the enclosing procedure or function. Sub function definition starts with the FUNCTION key word. Here is a sample sc... 2018-03-18, 3422🔥, 0💬

Export Data to an XML File in Oracle
How To Export Data to an XML File in Oracle? If you want to export data from a table to a file in XML format, you can use the following steps: Right-click the table name, EMPLOYEES, in the object tree view. Select Export. Select XML. The Export Data window shows up. Click Format tab. Select Format a... 2019-01-12, 3419🔥, 0💬

IS_IPV4() - Detecting IPv4 Address
How to detect an IPv4 Address using the IS_IPV4() function? IS_IPV4(ip) is a MySQL built-in function that returns 1 if the given value is a valid IPv4 address, 0 otherwise. For example: SELECT IS_IPV4('10.0.5.9'), IS_IPV4('10.0.5.256'); -- +---------------------+------- ----------------+-- | IS_IPV4... 2026-02-02, 3418🔥, 0💬

Return Top 5 Rows in Oracle
How To Return Top 5 Rows in Oracle? If you want the query to return only the first 5 rows, you can use the pseudo column called ROWNUM in the WHERE clause. ROWNUM contains the row number of each returning row from the query. The following statement returns the first 5 rows from the employees table: ... 2019-09-16, 3418🔥, 0💬

"RIGHT OUTER JOIN ... ON" - Writing Queries with Right Outer Joins in SQL Server
How To Write a Query with a Right Outer Join in SQL Server? If you want to query from two tables with a right outer join, you can use the RIGHT OUTER JOIN ... ON clause in the FROM clause. The following query returns output with a right outer join from two tables: fyi_links and fyi_rates. The join c... 2016-10-30, 3416🔥, 0💬

Decrementing a Date by 1 in MySQL
How To Decrement Dates by 1 in MySQL? If you have a date, and you want to decrement it by 1 day, you can use the DATE_SUB(date, INTERVAL 1 DAY) function. You can also use the date interval subtraction operation as "date - INTERVAL 1 DAY". The tutorial exercise below gives you some good examples: SEL... 2017-12-26, 3415🔥, 0💬

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General MySQL Oracle SQL Server