General MySQL Oracle SQL Server

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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, 3075🔥, 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, 3071🔥, 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, 3069🔥, 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, 3066🔥, 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, 3064🔥, 0💬

Dropped Tables with Indexes in Oracle
What Happens to Indexes If You Drop a Table in Oracle? If you drop a table, what happens to its indexes? The answer is that if a table is dropped, all its indexes will be dropped too. Try the following script to see yourself: CREATE TABLE student (id NUMBER(5) PRIMARY KEY, first_name VARCHAR(80) NOT... 2019-04-22, 3063🔥, 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, 3057🔥, 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, 3053🔥, 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, 3051🔥, 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, 3050🔥, 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, 3049🔥, 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, 3046🔥, 0💬

Create a Stored Procedure in Oracle
How To Create a Stored Procedure in Oracle? A stored procedure is a procedure with a specified name and stored into the current database. If you want to create a stored procedure, you can use the CREATE PROCEDURE statement. The example script below creates a stored procedure: SQL&gt; CREATE PROC... 2018-11-11, 3046🔥, 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, 3044🔥, 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, 3044🔥, 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, 3040🔥, 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, 3036🔥, 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, 3036🔥, 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, 3030🔥, 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, 3027🔥, 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, 3012🔥, 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, 3012🔥, 0💬

Loading and Exporting Data in Oracle
Where to find answers to frequently asked questions on Loading and Exporting Data in Oracle? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Loading and Exporting Data in Oracle. Clear answers are provided with tutorial exercises on saving data as... 2018-06-27, 3010🔥, 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, 3010🔥, 0💬

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General MySQL Oracle SQL Server