General MySQL Oracle SQL Server

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Error: Cannot Identify/Lock Data File in Oracle
What Happens If You Lost a Data File in Oracle? After you shutting down an Oracle database, you accidently deleted a data file from the operating system. If you try to start the database again you will get error when Oracle tries to open the database after mounting the database. The following tutori... 2019-04-09, 2885🔥, 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, 2881🔥, 0💬

What Is a Subquery in Oracle
What Is a Subquery in Oracle? A subquery is a SELECT statement used as part of the selection criteria of the main SELECT statement. The subquery specified in the WHERE clause will be evaluated repeated on each row of the selection base table. The output of the subquery will be used in the final eval... 2019-09-27, 2875🔥, 0💬

Differences between NUMBER and BINARY_FLOAT in Oracle
What Are the Differences between NUMBER and BINARY_FLOAT in Oracle? The main differences between NUMBER and BINARY_FLOAT are: NUMBER stores values as fixed-point numbers using 1 to 22 bytes. BINARY_FLOAT stores values as single precision floating-point numbers.   ⇒ Differences between DATE and TIMES... 2020-04-25, 2870🔥, 0💬

Start 10g XE Server in Oracle
How To Start Your 10g XE Server in Oracle? Go to the Start menu, select All Programs, Oracle Database 10g Express Edition, and Start Database.   ⇒ Memory Usage of 10g XE Server in Oracle ⇐ Shutdown 10g XE Server in Oracle ⇑ Introduction to Oracle Database 10g Express Edition ⇑⇑ Oracle Database Tut... 2020-10-10, 2868🔥, 0💬

Managing Oracle Database Tables
Where to find answers to frequently asked questions on Managing Oracle Database Tables? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Managing Oracle Database Tables. Clear answers are provided together with tutorial exercises to help beginners ... 2019-06-11, 2867🔥, 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, 2866🔥, 0💬

Show Dropped Tables in Recycle Bin in Oracle
How To View the Dropped Tables in Your Recycle Bin in Oracle? You can look what's in your recycle bin through the predefined view called RECYCLEBIN. You can use the SELECT statement to list the dropped tables as shown in the following script: SQL&gt; connect HR/fyicenter Connected. SQL&gt; C... 2019-05-14, 2861🔥, 0💬

Differences between CHAR and NCHAR in Oracle
What Are the Differences between CHAR and NCHAR in Oracle? Both CHAR and NCHAR are fixed length character data types. But they have the following differences: CHAR's size is specified in bytes by default. NCHAR's size is specified in characters by default. A character could be 1 byte to 4 bytes long... 2020-04-25, 2847🔥, 0💬

Use SYS Account to Connect to the Server in Oracle
How To Connect to the Server with User Account: SYS in Oracle? SYS is a very special user account. It has been associated with the highest privilege call SYSDBA. Normally, you should not connect to the server with SYS. But if you want to use it, you need to use a special connect command: &gt;cd ... 2019-07-21, 2846🔥, 0💬

Differences between CHAR and VARCHAR in Oracle
What Are the Differences between CHAR and VARCHAR2 in Oracle? The main differences between CHAR and VARCHAR2 are: CHAR stores values in fixed lengths. Values are padded with space characters to match the specified length. VARCHAR2 stores values in variable lengths. Values are not padded with any cha... 2020-04-25, 2845🔥, 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, 2842🔥, 0💬

Numeric Literals in Oracle
How To Write Numeric Literals in Oracle? Numeric literals can coded as shown in the following samples: SELECT 255 FROM DUAL -- An integer 255 SELECT -6.34 FROM DUAL -- A regular number -6.34 SELECT 2.14F FROM DUAL -- A single-precision floating point 2.14 SELECT -0.5D FROM DUAL -- A double-precision... 2020-04-14, 2839🔥, 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, 2824🔥, 0💬

Select Some Rows from a Table in Oracle
How To Select Some Rows from a Table in Oracle? If you don't want select all rows from a table, you can specify a WHERE clause to tell the query to return only the rows that meets the condition defined in the WHERE clause. The following select statement only returns rows that has department name sta... 2019-12-19, 2815🔥, 0💬

Instance Settings Stored in SPFile in Oracle
Where Are the Settings Stored for Each Instance in Oracle? Settings for each instance are stored in a file called Server Parameter File (SPFile). Oracle supports two types of parameter files, Text type, and Binary type. parameter files should be located in $ORACLE_HOME\database directory. A paramete... 2020-09-15, 2813🔥, 0💬

Create a New Data File in Oracle
How To Create a New Oracle Data File in Oracle? There is no dedicated statement to create a data file. Data files are created as part of statements that manages other data structures, like tablespace and database.   ⇒ Create a New Tablespace in Oracle ⇐ Show All Data Files in the Current Database i... 2019-04-13, 2813🔥, 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, 2805🔥, 0💬

Divide Query Output into Groups in Oracle
How To Divide Query Output into Groups in Oracle? You can divide query output into multiple groups with the GROUP BY clause. It allows you specify a column as the grouping criteria, so that rows with the same value in the column will be considered as a single group. When the GROUP BY clause is speci... 2019-11-21, 2803🔥, 0💬

Date and Time Interval Literals in Oracle
How To Write Date and Time Interval Literals in Oracle? Date and time interval literals can coded as shown in the following samples: SELECT DATE '2002-10-03' + INTERVAL '123-2' YEAR(3) TO MONTH FROM DUAL -- 123 years and 2 months is added to 2002-10-03 03-DEC-25 SELECT DATE '2002-10-03' + INTERVAL '... 2020-03-25, 2802🔥, 0💬

Use Windows User to Connect to the Server in Oracle
How To Use Windows User to Connect to the Server in Oracle? During the installation process, 10g XE will create a special Windows user group called ORA_DBA, and put your Windows user into this group. Any Windows users in this group can be connected to Oracle server with SYSDBA privilege without any ... 2019-07-21, 2800🔥, 0💬

Declare Local Variables in Oracle
How To Declare a Local Variable in Oracle? A local variable can be defined in the declaration part with a declaration statement, which is a variable name followed a data type identifier. Below are some examples of declaration statements: PROCEDURE proc_var_1 AS domain VARCHAR2(80); price REAL; is_fo... 2018-11-17, 2799🔥, 0💬

Add a New Column to an Existing Table with a Default Value in Oracle
How To Add a New Column to an Existing Table with a Default Value in Oracle? If you want to add a new column to an existing table, and insert a default value in this column on all existing data rows, you can use the ALTER TABLE ... ADD statement with the DEFAULT clause. Here is an example script: SQ... 2019-05-25, 2796🔥, 0💬

Login to Server without an Instance in Oracle
How To Login to the Server without an Instance in Oracle? If your default instance is in trouble, and you can not use the normal login process to reach the server, you can use a special login to log into the server without any instance. Here is how to use SQL*Plus to log in as a system BDA: &gt;... 2020-09-15, 2793🔥, 0💬

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General MySQL Oracle SQL Server