General MySQL Oracle SQL Server

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Selecting Some Specific Columns from a Table in SQL Server
How To Select Some Specific Columns from a Table in a Query in SQL Server? If you want explicitly tell the query to return some specific columns, you can specify the column names in the SELECT clause. The following select statement returns only three columns, "id", "created" and "url" from the table... 2016-10-26, 3711🔥, 0💬

What Is a READ WRITE Transaction in Oracle
What Is a READ WRITE Transaction in Oracle? A READ WRITE transaction is a transaction in which the read consistency is set at the statement level. In a READ WRITE transaction, a logical snapshot of the database is created at the beginning of the execution of each statement and released at the end of... 2019-08-23, 3709🔥, 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, 3709🔥, 0💬

EXECUTE - Executing Stored Procedures in SQL Server
How To Execute a Stored Procedure in SQL Server Transact-SQL? If you want execute a stored procedure created previously, you can use the EXECUTE statement in the following formats: EXEC procedure_name; EXECUTE procedure_name; The key word EXEC is actually optional. So you can execute a stored proced... 2017-01-05, 3706🔥, 0💬

Convert Times to Character Strings in Oracle
How To Convert Times to Character Strings in Oracle? You can convert dates to characters using the TO_CHAR() function as shown in the following examples: SELECT TO_CHAR(SYSDATE, 'HH:MI:SS') FROM DUAL; 04:49:49 SELECT TO_CHAR(SYSDATE, 'HH24:MI:SS.FF') FROM DUAL; -- Error: SYSDATE has no fractional se... 2019-12-02, 3704🔥, 0💬

List All Existing Databases in MySQL
How To Get a List of Databases from MySQL Servers in MySQL? Once you got a MySQL server connection object successfully, you need to know what databases are available on the server and which database you should use to manage your tables and data. To get a list of all available databases on your MySQL... 2017-11-11, 3702🔥, 0💬

Create an Array in PL/SQL in Oracle
How To Create an Array in PL/SQL in Oracle? If you want create an array data structure, you can use the collection type VARRAY. VARRAY stands for Variable Array. Here is a sample script on how to use VARRAY: SQL&gt; set serveroutput on; SQL&gt; DECLARE 2 TYPE list IS VARRAY(3) OF VARCHAR(16)... 2019-03-08, 3698🔥, 0💬

What Is ODBC in Oracle
What Is Open Database Communication (ODBC) in Oracle? ODBC, Open Database Communication, a standard API (application program interface) developed by Microsoft for Windows applications to communicate with database management systems. Oracle offers ODBC drivers to allow Windows applications to connect... 2020-05-15, 3694🔥, 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, 3694🔥, 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, 3683🔥, 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, 3682🔥, 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, 3678🔥, 0💬

UPDATE Using Data from Other Tables in MySQL
How To Use Values from Other Tables in UPDATE Statements in MySQL? If you want to update values in one table with values from another table, you can use a subquery as an expression in the SET clause. The subquery should return only one row for each row in the update table that matches the WHERE clau... 2018-01-13, 3677🔥, 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, 3677🔥, 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, 3676🔥, 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, 3675🔥, 0💬

"DISABLE TRIGGER" - Disabling Triggers in SQL Server
How To Disable Triggers using "DISABLE TRIGGER" in SQL Server? If want to stop the execution of an existing trigger temporarily, you can use the "DISABLE TRIGGER" statement to disable it. The disabled trigger will be kept in the database. If you want to resume the execution of a disabled trigger, yo... 2016-10-24, 3665🔥, 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, 3661🔥, 0💬

Analyze Tables with "mysqlcheck" Command in MySQL
How To Analyze Tables with "mysqlcheck" in MySQL? If you want analyze tables with "mysqlcheck", you need to use the "--analyze" option. The following tutorial exercise shows you how to analyze all tables in "mysql" database: &gt;cd \mysql\bin &gt;mysqlcheck -u root --analyze mysql mysql.colu... 2018-02-28, 3656🔥, 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, 3653🔥, 0💬

Setup Autotrace for a User Account in Oracle
How To Set Up Autotrace for a User Account in Oracle? If an Oracle user wants to use the autotrace feature, you can use the tutorial as an example to create the required table PLAN_TABLE, the required security role PLUSTRACE, and grant the role to that user: SQL&gt; CONNECT HR/retneciyf SQL&... 2020-06-08, 3648🔥, 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, 3648🔥, 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, 3645🔥, 0💬

Character Strings and Binary Strings in SQL Server Transact-SQL
Where to find answers to frequently asked questions on Character Strings and Binary Strings in SQL Server Transact-SQL? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Character Strings and Binary Strings in SQL Server Transact-SQL. Clear answers ... 2017-03-11, 3645🔥, 0💬

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General MySQL Oracle SQL Server