General MySQL Oracle SQL Server

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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, 3396🔥, 0💬

Built-in Tablespaces in a Database in Oracle
What Are the Predefined Tablespaces in a Database in Oracle? When you create a new database, Oracle server will create 4 required tablespaces for the new database: SYSTEM Tablespace - Every Oracle database contains a tablespace named SYSTEM, which Oracle creates automatically when the database is cr... 2019-01-20, 3395🔥, 0💬

Assign a Tablespace to a User in Oracle
How To Assign a Tablespace to a Users in Oracle? When you create a new user, Oracle will assign the SYSTEM tablespace to the user by default. If you want to change this, you can assign a different table space to a user using the ALTER USER command. The following tutorial exercise changes user dev's ... 2019-06-29, 3380🔥, 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, 3377🔥, 0💬

What Is SQL Standard in Oracle
What Is SQL Standard in Oracle? SQL, SEQUEL (Structured English Query Language), is a language for RDBMS (Relational Database Management Systems). SQL was developed by IBM Corporation. SQL became an ANSI standard, called SQL-87, in 1986. ISO made a major revision, called SQL-92, in 1992. The latest ... 2020-05-29, 3372🔥, 0💬

Delete a Column in an Existing Table in Oracle
How To Delete a Column in an Existing Table in Oracle? If you have an existing column in a table and you need that column any more, you can delete it with ALTER TABLE ... DROP COLUMN statement. Here is an example SQL script: SQL&gt; CREATE TABLE emp_dept_90 2 AS SELECT * FROM employees WHERE dep... 2019-05-25, 3372🔥, 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, 3371🔥, 0💬

ALTER TABLE - Add a New Column in Oracle
How To Add a New Column to an Existing Table in Oracle? If you have an existing table with existing data rows, and want to add a new column to that table, you can use the ALTER TABLE ... ADD statement to do this. Here is an example script: SQL&gt; connect HR/fyicenter Connected. SQL&gt; CREA... 2020-02-29, 3369🔥, 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, 3365🔥, 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, 3359🔥, 0💬

Oracle Built-in Data Types in Oracle
What Are the Oracle Built-in Data Types in Oracle? There are 20 Oracle built-in data types, divided into 6 groups: Character Datatypes - CHAR, NCHAR, NVARCHAR2, VARCHAR2 Number Datatypes - NUMBER, BINARY_FLOAT, BINARY_DOUBLE Long and Row Datatypes - LONG, LONG RAW, RAW Datetime Datatypes - DATE, TIM... 2020-05-29, 3357🔥, 0💬

Change Settings in Binary SPFile in Oracle
What To Do If the Binary SPFile Is Wrong for the Default Instance in Oracle? Let's say the SPFile for the default instance is a binary file, and some settings are wrong in the SPFile, like SGA setting is bellow 20MB, how do you change a setting in the binary file? This seems to be a hard task, becau... 2020-09-15, 3356🔥, 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, 3356🔥, 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, 3356🔥, 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, 3354🔥, 0💬

Help at the SQL Prompt in Oracle
How To Get Help at the SQL Prompt in Oracle? Once SQL*Plus is started, you will get a SQL prompt like this: SQL&gt;. This where you can enter commands for SQL*Plus to run. To get help information at the SQL prompt, you can use the HELP command as shown in the following tutorial example: SQL&... 2020-08-25, 3351🔥, 0💬

Working with Cursors in Oracle PL/SQL
Where to find answers to frequently asked questions on Working with Cursors in Oracle PL/SQL? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Working with Cursors in Oracle PL/SQL. Clear answers are provided with tutorial exercises on defining, op... 2018-02-01, 3350🔥, 0💬

Date and Time Literals in Oracle
How To Write Date and Time Literals in Oracle? Date and time literals can coded as shown in the following samples: SELECT DATE '2002-10-03' FROM DUAL -- ANSI date format 03-OCT-02 SELECT TIMESTAMP '1997-01-31 09:26:50.124' FROM DUAL 31-JAN-97 09.26.50.124000000 AM -- This is ANSI format   ⇒ Date and... 2020-04-14, 3348🔥, 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, 3347🔥, 0💬

Transaction Rollback When Session Killed in Oracle
What Happens to the Current Transaction If the Session Is Killed in Oracle? If a session is killed by the DBA, the current transaction in that session will be rolled back and ended. All the database changes made in the current transaction will be removed. This is called an implicit rollback when ses... 2019-08-23, 3346🔥, 0💬

What Is a Directory Object in Oracle
What Is a Directory Object in Oracle? A directory object is a logical alias for a physical directory path name on the operating system. Directory objects can be created, dropped, and granted access permissions to different users. The following tutorial exercise shows you some good examples: &gt;... 2016-10-15, 3342🔥, 0💬

Create an Initialization Parameter File in Oracle
How To Create an Initialization Parameter File in Oracle? This is Step 3. To run an Oracle database as an Oracle instance, you need to create an initialization parameter file, which contains a set of initialization parameters. The easiest way to create an initialization parameter file to copy from t... 2019-04-03, 3339🔥, 0💬

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, 3337🔥, 0💬

Use LIKE Conditions in Oracle
How To Use LIKE Conditions in Oracle? LIKE condition is also called pattern patch. There 3 main rules on using LIKE condition: '_' is used in the pattern to match any one character. '%' is used in the pattern to match any zero or more characters. ESCAPE clause is used to provide the escape character... 2020-03-15, 3336🔥, 0💬

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General MySQL Oracle SQL Server