General MySQL Oracle SQL Server

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"TOP" - Return the Top 5 Rows from a SELECT Query in SQL Server
How To Return the Top 5 Rows from a SELECT Query in SQL Server? If you want the query to return only the first 5 rows, you can use the "TOP 5" clause. The TOP clause takes one parameter to indicate how many top rows to return. The following statements returns the first 5 rows and 3 rows from the fyi... 2016-10-29, 482👍, 0💬

"GROUP BY" - Dividing Query Output into Multiple Groups in SQL Server
How To Divide Query Output into Multiple Groups with the GROUP BY Clause in SQL Server? Sometimes, you want to divide the query output into multiple groups, and apply group functions on each individual groups. Dividing query output into multiple groups can be done with the GROUP BY clause. Here is t... 2016-10-25, 482👍, 0💬

User Account and Attributes in Oracle
What Is a User Account in Oracle? A user account is identified by a user name and defines user's attributes, including the following: Password for database authentication Privileges and roles Default tablespace for database objects Default temporary tablespace for query processing work space   ⇒Mana... 2019-07-30, 481👍, 0💬

Subtracting a DATETIME Value from Another DATETIME Value in SQL Server
Can a DATETIME Value Be Subtracted from Another DATETIME Value in SQL Server Transact-SQL? Can a datetime value be subtracted from another datetime value? The answer is yes. The subtract operation can be performed by the subtract operator (-) as: datetime1 - datetime2: Returning a DATETIME value cal... 2017-02-20, 481👍, 0💬

Create a Single Index for Multiple Columns in Oracle
How To Create a Single Index for Multiple Columns in Oracle? If you know a group of multiple columns will be always used together as search criteria, you should create a single index for that group of columns with the "ON table_name(col1, col2, ...)" clause. Here is an example of one index for two c... 2019-04-17, 480👍, 0💬

What Is SQL Standard in MySQL
What Is SQL Standard in MySQL? 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 r... 2018-04-21, 480👍, 0💬

SINGLE_USER/MULTI_USER - Database User Access Options in SQL Server
How to set database to be SINGLE_USER in SQL Server? Databases in SQL Server have three user access options: MULTI_USER - All users that have the appropriate permissions to connect to the database are allowed. This is the default. SINGLE_USER - One user at a time is allowed to connect to the databas... 2016-11-20, 479👍, 0💬

Deleting Multiple Rows with One DELETE Statement in SQL Server
How To Delete Multiple Rows with One DELETE Statement in SQL Server? 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: -- view rows to be dele... 2016-10-30, 477👍, 0💬

Categories of Functions Based on Return Modes in SQL Server
How Many Categories of Functions based Their Return Modes in SQL Server Transact-SQL? SQL Server supports 2 categories of user defined functions based on their return modes: 1. Scalar-valued Functions - A function that returns a single value. Scalar-valued functions can be used in scalar expressions... 2016-12-18, 476👍, 0💬

Adding More Test Data for Query Statements in SQL Server
How To Add More Data to the Testing Table in SQL Server? If you want to continue with other tutorial exercises in this FAQ collection, you need to add more data to the testing table. Follow the script below to add a new column and more rows: ALTER TABLE fyi_links ADD tag VARCHAR(8) GO UPDATE fyi_lin... 2016-10-26, 476👍, 0💬

Default Schema of Your Login Session in SQL Server
What Is the Default Schema of Your Login Session in SQL Server? When you login to a SQL Server and select a database to use, SQL Server will assign your login session a default schema. The schema name can be omitted when you refer to objects in the default schema. Here is what you should remember ab... 2016-10-22, 476👍, 0💬

"OPEN" - Executing the Query of a Cursor in SQL Server
How To Execute the Cursor Queries with "OPEN" Statements in SQL Server Transact-SQL? Once a cursor is declared, you need to execute the query attached to the cursor so that the result set returned from the query can be accessed through the cursor. To execute the cursor query, you should use the OPEN... 2016-10-17, 476👍, 0💬

Writing Date and Time Literals in MySQL
How To Write Date and Time Literals in MySQL? MySQL offers a number of formats for you to use to enter date and time literals: ANSI standard format: "YYYY-MM-DD HH:MM:SS". Non-standard limiters. Like: "YYYY/MM/DD HH^MM^SS" or "YYYY.MM.DD HH-MM-SS". No limiters. Like: "YYYYMMDD" for a date or "HHMMSS... 2017-12-26, 475👍, 0💬

Security Principals Used in SQL Server 2005 in SQL Server
What Are Security Principals Used in SQL Server 2005 in SQL Server? SQL Server 2005 supports several basic security principals located at different levels: Windows-Level Principals: Windows Local Login and Windows Network Domain Login - Used to control accesses to SQL Server instances. SQL Server-Le... 2016-10-20, 475👍, 0💬

"DROP TABLE" - Deleting Existing Tables in SQL Server
How To Drop an Existing Table with "DROP TABLE" Statements in SQL Server? If you want to delete an existing table and its data rows, you can use the "DROP TABLE" statement as shown in the tutorial script below: SELECT * FROM tipBackup GO id subject description create_date 1 Learn SQL Visit dev.fyice... 2016-11-15, 474👍, 0💬

Mixing Group Functions with Non-group Selection Fields in SQL Server
Can Group Functions Be Mixed with Non-group Selection Fields in SQL Server? If a group function is used in the SELECT clause, all other selection fields must be group level fields. Non-group fields can not be mixed with group fields in the SELECT clause. The script below gives you an example of inva... 2016-10-25, 473👍, 0💬

Getting a List of All Databases on the Server in SQL Server
How to get a list all databases on the SQL server in SQL Server? If you don't remember database names you have created, you can get a list of all databases on the server by query the "sys.databases" view as shown in this tutorial example: CREATE DATABASE FyiCenterData GO SELECT name, database_id, cr... 2016-11-24, 471👍, 0💬

"DROP SCHEMA" - Dropping an Existing Schema in SQL Server
How To Drop an Existing Schema in SQL Server? If you want to delete a schema, you need to move all objects out of that schema, then use the "DROP SCHEMA" statement to delete the schema. The tutorial exercise below shows you how to drop schema "fyi": -- Login with "sa" USE FyiCenterData; GO -- Drop f... 2016-10-20, 470👍, 0💬

OFFLINE - Taking a database offline in SQL Server
How to set a database state to OFFLINE in SQL Server? If you want to move database physical files, you should take the database offline by using the "ALTER DATABASE" statement with the following syntax: ALTER DATABASE database_name SET OFFLINE The following tutorial example will bring "FyiCenterComD... 2016-11-20, 469👍, 0💬

UPDATE Subquery Returning No Rows in SQL Server
What Happens If the UPDATE Subquery Returns No Rows in SQL Server? If you use a subquery to assign new values in the SET clause in an UPDATE statement, and the subquery returns no rows for an outer row, SQL Server will provide a NULL value to the SET clause. The tutorial exercise below shows you a g... 2016-11-02, 469👍, 0💬

What Are Triggers in SQL Server
What Are Triggers in SQL Server? A trigger is a special kind of stored procedure that automatically executes when an event occurs in the database server. A trigger is really an event handler. SQL Server allows users to create triggers (event handlers) for 3 types of events: DML Event - Occurs when a... 2016-10-25, 467👍, 0💬

How Data Locks Are Respected in Oracle
How Data Locks Are Respected in Oracle? Here are the rules on how data locks are respected: All statements ignore data locks owned its own transaction. SELECT query statements ignores data locks owned by any transactions. INSERT, UPDATE, and DELETE statements in a READ COMMITTED transaction will wai... 2019-08-08, 466👍, 0💬

Using User Defined Functions in Expressions in SQL Server
How To Use User Defined Functions in Expressions in SQL Server Transact-SQL? An user defined function must return a value, which can be used in any expression as long as the return value data type matches the expression. To execute a user defined function and use its return value in an expression, y... 2016-12-24, 465👍, 0💬

Using Subqueries with the IN Operators in SQL Server
How To Use Subqueries with the IN Operators in SQL Server? A subquery can be used with the IN operator as "expression IN (subquery)". The subquery should return a single column with one or more rows to form a list of values to be used by the IN operation. The following tutorial exercise shows you ho... 2016-10-29, 465👍, 0💬

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General MySQL Oracle SQL Server