General MySQL Oracle SQL Server

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Rename a Column in an Existing Table in Oracle
How To Rename a Column in an Existing Table in Oracle? Let's say you have an existing with an existing column, but you don't like the name of that column, can you rename that column name? The answer is yes. You can use the ALTER TABLE ... RENAME COLUMN statement to do this. See the following SQL scr... 2019-05-25, 1586🔥, 0💬

Define Anonymous Procedures with Variables in Oracle
How To Define an Anonymous Procedure with Variables in Oracle? Anonymous procedure is a procedure without any name. If you have some variables to declare, you can define an anonymous procedure by using the DECLARE keyword in SQL*Plus as shown in the following tutorial script: SQL&gt; set servero... 2018-01-27, 1586🔥, 0💬

Delete a User Account in Oracle
How To Delete a User Account in Oracle? If you want to delete a user account and its associated schema, you can log in as SYSTEM and use the DROP USER command as shown in the following example: &gt;.\bin\sqlplus /nolog SQL&gt; connect SYSTEM/fyicenter Connected. SQL&gt; DROP USER DEV CAS... 2019-07-09, 1585🔥, 0💬

Date and Time Data Types in SQL Server Transact-SQL
What are date and time data types supported in SQL Server Transact-SQL? Date and time data types are used to hold dates and times. There are 6 date and time data types supported in SQL Server Transact-SQL: 1. DATETIME - Use to hold date and times with a large precision using 8-byte storages: 4 bytes... 2017-04-15, 1585🔥, 0💬

Using Old Values to Define New Values in UPDATE Statements in SQL Server
How to use old values to define new values in UPDATE statements in SQL Server? If a row matches the WHERE clause in a UPDATE statement, existing values in this row can be used in expressions to provide new values in the SET clause. Existing values are represented by column names in the expressions. ... 2016-11-02, 1585🔥, 0💬

Counting Groups Returned with the GROUP BY Clause in Oracle
How To Count Groups Returned with the GROUP BY Clause in Oracle? If you use the COUNT(*) function on groups returned with the GROUP BY clause, it will count the number of rows within each group, not the number of groups. If you want to count the number of groups, you can put the GROUP BY query into ... 2019-09-16, 1584🔥, 0💬

Convert Character Types to Numeric Types in Oracle
How To Convert Character Types to Numeric Types in Oracle? You can convert character types to numeric types in two ways: Explicitly by using TO_NUMBER() function. Implicitly by putting character data in a numeric operation. The sample script below shows you how to convert character types to numeric ... 2018-11-17, 1584🔥, 0💬

Starting mysqld to Support BDB Storage Engine in MySQL
How To Start mysqld to Support the BDB Storage Engine in MySQL? The default "mysqld" program does not support the BDB storage engine. If you want to use the BDB storage engine, you can start MySQL server with the "mysqld-max" program. The tutorial exercise below shows you how to start "mysqld-max" a... 2017-08-13, 1583🔥, 0💬

Transaction Waiting for a Data Lock in MySQL
How Long a Transaction Will Wait for a Data Lock in MySQL? If you issue a UPDATE or DELETE statement on a row that has an exclusive lock owned by another session, your statement will be blocked to wait for the other session to release the lock. But the wait will be timed out after the predefined inn... 2017-04-28, 1583🔥, 0💬

What Is CSV in MySQL
What Is CSV in MySQL? CSV (Comma Separated Values) is a file format used to store database table contents, where one table row is stored as one line in the file, and each data field is separated with comma.   ⇒ What Is Transaction in MySQL ⇐ What Is BDB in MySQL ⇑ Database Basics and Terminologies ... 2016-10-16, 1583🔥, 0💬

What Are DDL Statements in Oracle
What Are DDL Statements in Oracle? DDL (Data Definition Language) statements are statements to create and manage data objects in the database. The are 3 primary DDL statements: CREATE - Creating a new database object. ALTER - Altering the definition of an existing data object. DROP - Dropping an exi... 2020-02-29, 1582🔥, 0💬

Managing Tables and Columns in SQL Server
Where to find answers to frequently asked questions on Managing Tables and Columns in SQL Server? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Managing Tables and Columns in SQL Server. Clear answers are provided with tutorial exercises on crea... 2016-11-20, 1582🔥, 0💬

What Is "mysql" Command in MySQL
What Is "mysql" in MySQL? "mysql" is a command-line interface for end users to manage user data objects. You can use "mysql" to run any standard SQL statements against the server. For example, you use the following SQL statements to manage tables and table rows: "CREATE TABLE links (name VARCHAR(80)... 2018-05-19, 1581🔥, 0💬

Create an Oracle Database Manually in Oracle
How To Create an Oracle Database Manually in Oracle? Based on Oracle's Administrator Guide, there are 11 steps to create a database with the CREATE DATABASE statement: Step 1: Decide on Your Instance Identifier (SID) Step 2: Establish the Database Administrator Authentication Method Step 3: Create t... 2019-04-03, 1580🔥, 0💬

Create a New Table by Selecting Rows from Another Table in Oracle
How To Create a New Table by Selecting Rows from Another Table in Oracle? Let's say you have a table with many data rows, now you want to create a backup copy of this table of all rows or a subset of them, you can use the CREATE TABLE...AS SELECT statement to do this. Here is an example script: &... 2019-06-01, 1579🔥, 0💬

Loading Data Files with "mysqlimport" Command in MySQL
How To Load Data Files into Tables with "mysqlimport" in MySQL? If you want to load a data file directly into a table, you need to prepare the data file as one line per data row, and use tab character as the column delimiter. The data file name should match the target table name. The following is a ... 2018-04-28, 1579🔥, 0💬

Experiment with Data Locks in MySQL
How To Experiment Data Locks in MySQL? If you want to have some experience with data locks, you can create two windows running two mysql transactions in two sessions. In session 1, you can run a UPDATE statement with REPEATABLE READ transaction isolation level to create an exclusive lock. Before com... 2017-04-28, 1579🔥, 0💬

Restrictions on External Table Columns in Oracle
What Are the Restrictions on External Table Columns in Oracle? When creating external table columns, you need to watch out some restrictions: "PRIMARY KEY" is not allowed. "NOT NULL" is not allowed. "DEFAULT value" is not allowed.   ⇒ What Is a Directory Object in Oracle ⇐ Load Data through Externa... 2016-11-27, 1579🔥, 0💬

Shutdown 10g XE Server from Commmand Line in Oracle
How To Shutdown Your 10g XE Server from Command Line in Oracle? You can shutdown your 10g XE server from command line by: Open a command line window. Change directory to \oraclexe\app\oracle\product\1 0.2.0\server\BIN\.Run StopDB.bat. The batch file StopDB.bat contains: net stop OracleServiceXE   ⇒ ... 2020-10-10, 1578🔥, 0💬

Add Another Datafile to a Tablespace in Oracle
How To Add Another Datafile to a Tablespace in Oracle? If you created a tablespace with a data file a month ago, now 80% of the data file is used, you should add another data file to the tablespace. This can be done by using the ALTER TABLESPACE ... ADD DATAFILE statement. See the following sample s... 2019-04-09, 1578🔥, 0💬

Establish Administrator Authentication to the Server in Oracle
How To Establish Administrator Authentication to the Server in Oracle? This is Step 2. There are two ways to establish administrator authentication to a new database. Use a password file. Use operating system (OS) authentication. Using OS authentication is easier on Windows system. If you used your ... 2019-04-03, 1578🔥, 0💬

Define and Use Table Alias Names in Oracle
How To Define and Use Table Alias Names in Oracle? When column names need to be prefixed with table names, you can define table alias name and use them to prefix column names as shown in the following select statement: SQL&gt; SELECT e.first_name, e.last_name, d.department_name FROM employees e ... 2019-10-27, 1575🔥, 0💬

Privilege to Create Indexes in Oracle
What Privilege Is Needed for a User to Create Indexes in Oracle? For a user to create indexes, he/she needs the same privilege as the creating tables. Just make sure he/she has the CREATE TABLE privilege. The following tutorial exercise gives you a good example on creating view privilege: &gt;.\... 2019-06-29, 1575🔥, 0💬

Privilege to Insert Rows in Another Schema in Oracle
What Privilege Is Needed for a User to Insert Rows to Tables in Another Schema in Oracle? For a user to insert rows into tables of someone else's schema, he/she needs the INSERT ANY TABLE privilege. The following tutorial exercise gives you a good example of granting "dev" to insert rows in "hr" sch... 2019-06-11, 1575🔥, 0💬

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General MySQL Oracle SQL Server