General MySQL Oracle SQL Server

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Sort Query Output in Descending Order in Oracle
How To Sort Query Output in Descending Order in Oracle? If you want to sort a column in descending order, you can specify the DESC keyword in the ORDER BY clause. The following SELECT statement first sorts the department in descending order, then sorts the salary in ascending order: SQL&gt; SELE... 2019-12-19, 1525🔥, 0💬

Exact Numeric Data Types in SQL Server Transact-SQL
What are exact numeric data types supported in SQL Server Transact-SQL? Exact numeric data types are used to hold numeric values truncated to a specific precision and scale. There are 8 different exact numeric data types supported in SQL Server Transact-SQL: 1. BIGINT - Used to hold big integers wit... 2017-04-22, 1525🔥, 0💬

DECLARE Statements in SQL Server Transact-SQL
How to declare a variable in SQL Server Transact-SQL? How to use the DECLARE statements? In Transact-SQL, you must use DECLARE statements to declare variables. Declaring a variable is to define the variable name and the variable data type. In Transact-SQL, you can: Declare a single variable in a sin... 2017-04-04, 1525🔥, 0💬

String Type Conversion During Concatenation in SQL Server
What Happens When Unicode Strings Concatenate with Non-Unicode Strings in SQL Server Transact-SQL? If a Unicode string NVARCHAR is concatenated with a non-Unicode string VARCHAR, SQL Server will implicitly convert the non-Unicode string to Unicode string for concatenation. DECLARE @regcode VARCHAR(4... 2017-03-11, 1525🔥, 0💬

Invoke Built-in Functions in PL/SQL in Oracle
How To Invoke Built-in Functions in PL/SQL in Oracle? Of course, you can invoke SQL functions in SQL statements. But many SQL functions can also be executed in regular PL/SQL statements, as shown in the following sample script: DECLARE now DATE; id NUMBER; str VARCHAR2(40); BEGIN now := SYSDATE; DBM... 2018-09-13, 1524🔥, 0💬

NULL Values Involved in Boolean Operations in SQL Server
What Happens If NULL Values Are Involved in Boolean Operations in SQL Server Transact-SQL? If NULL values are involved in Boolean operations, the result will vary depending on the operator type. For AND operator, FALSE takes precedence over NULL. The result can be summarized in a table below: AND TR... 2017-02-03, 1524🔥, 0💬

Adding Address Records into AdventureWorksLT in SQL Server
How to add an address record into AdventureWorksLT in SQL Server? To find out if we can add data into AdventureWorksLT or not, you can try to add an address record into the "SalesLT.Address" in AdventureWorksLT: USE AdventureWorksLT GO INSERT SalesLT.Address (AddressLine1, City, StateProvince, Count... 2016-12-02, 1524🔥, 0💬

What Are DDL Statements in MySQL
What Are DDL Statements in MySQL? 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 exis... 2018-03-10, 1523🔥, 0💬

Cursor Variable Easier to Use than Cursor in Oracle
Why Cursor Variables Are Easier to Use than Cursors in Oracle? Cursor variables are easier to use than cursors because: Cursor variables are easier to define. No need to give a specific query statement. Cursor variables are easier to open. You can specify the query dynamically at the time of open. C... 2018-06-27, 1522🔥, 0💬

What Is InnoDB in MySQL
What Is InnoDB in MySQL? InnoDB is a transaction safe storage engine developed by Innobase Oy (an Oracle company now).   ⇒ What Is BDB in MySQL ⇐ What Is MyISAM in MySQL ⇑ Database Basics and Terminologies in MySQL ⇑⇑ MySQL Database Tutorials 2017-07-03, 1522🔥, 0💬

Use Group Functions in the SELECT Clause in Oracle
How To Use Group Functions in the SELECT Clause in Oracle? If group functions are used in the SELECT clause, they will be used on the rows that meet the query selection criteria, the output of group functions will be returned as output of the query. The following select statement returns 4 values ca... 2019-11-21, 1521🔥, 0💬

Show Existing Locks on the Database in Oracle
How To View Existing Locks on the Database in Oracle? As can see from the pervious tutorial exercise, performance of the second session is greatly affected by the data lock created on the database. To maintain a good performance level for all sessions, you need to monitor the number of data locks on... 2019-08-08, 1521🔥, 0💬

Implicit Cursor in Oracle
What Is the Implicit Cursor in Oracle? The implicit cursor is the cursor automatically defined by PL/SQL for you. Whenever a SQL statement is executed, this cursor will be assigned to represent the execution of this statement. This implicit cursor is called SQL. It has many attributes representing s... 2018-09-13, 1521🔥, 0💬

"IS NULL" - Testing NULL Values in SQL Server
How To Test NULL Values Properly in SQL Server Transact-SQL? From previous tutorials, you learned that comparing expressions with NULL will always result NULL. So you can not use comparison operators to test if an expression represents a NULL value or not. To test expressions for NULL values, you sh... 2017-02-03, 1521🔥, 0💬

Deleting Multiple Rows from a Table in MySQL
How To Delete Multiple Rows from a Table in MySQL? 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: mysql&gt; SELECT id, url, notes, coun... 2018-01-08, 1520🔥, 0💬

What Are NULL Values in SQL Server
What Are NULL Values in SQL Server Transact-SQL? A NULL value is a special value that represents an unknown value. SQL Server supports NULL values with the following features: All data types used for table columns support NULL values. In another word, NULL values can be stored in database tables. In... 2017-02-05, 1520🔥, 0💬

What Is Index Fragmentation in SQL Server
What Is Index Fragmentation in SQL Server? Index fragmentation is a phenomena where index contents are no longer stored continuously in the storage. When index contents become scattered in the storage, fragmented, performance on index will degrade. If you want to see the fragmentation level of an in... 2016-11-08, 1520🔥, 0💬

Load Data from External Tables in Oracle
How To Load Data from External Tables to Regular Tables in Oracle? Once you have your data entered in a text file, and an external table defined to this text file, you can easily load data from this text file to a regular table. The following tutorial exercise shows you how to load data from the tex... 2016-10-15, 1519🔥, 0💬

Dividing Query Output into Groups in MySQL
How To Divide Query Output into Groups in MySQL? 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 that column will be considered as a single group. When the GROUP BY clause is speci... 2017-10-16, 1517🔥, 0💬

Quoting Text Values in MySQL
How To Quote Text Values in SQL Statements in MySQL? Text values in SQL statements should be quoted with single quotes ('). If the text value contains a single quote ('), it should be protected by replacing it with two single quotes (''). In SQL language syntax, two single quotes represents one sing... 2017-06-28, 1517🔥, 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, 1516🔥, 0💬

Create Additional Tablespaces in Oracle
How To Create Additional Tablespaces for an New Database in Oracle? This is Step 8. Creating additional tablespaces can be done by using the CREATE TABLESPACE statement as shown in the following sample script: SQL&gt; CREATE TABLESPACE users 2 DATAFILE '/oraclexe/oradata/FYI/users01 .dbf'SIZE 10... 2019-03-27, 1516🔥, 0💬

Relations between a Tablespace and Data Files in Oracle
How a Tablespace Is Related to Data Files in Oracle? Each tablespace in an Oracle database consists of one or more files called datafiles, which are physical structures that conform to the operating system in which Oracle is running.   ⇒ Relation between Database and Tablespaces in Oracle ⇐ Oracle ... 2019-01-20, 1516🔥, 0💬

Export Connection Information to a File in Oracle
How To Export Your Connection Information to a File in Oracle? SQL Developer allows you to export your connection information into an XML file. Here is how to do this: Right-click on Connections Select Export Connection... Enter File Name as: \temp\connections.xml Click OK Open \temp\connections.xml... 2018-10-08, 1516🔥, 0💬

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General MySQL Oracle SQL Server