General MySQL Oracle SQL Server

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Error: Single-Row Subquery Returns More Than One Row in Oracle
What Happens If the UPDATE Subquery Returns Multiple Rows in Oracle? If a subquery is used in a UPDATE statement, it must return exactly one row for each row in the update table that matches the WHERE clause. If it returns multiple rows, Oracle server will give you an error message. To test this out... 2020-01-21, 2646🔥, 0💬

What Are Indexes in SQL Server
What Are Indexes in SQL Server? An index is a secondary database object associated with a table to improve the retrieval performance of rows from that table. An index can be defined for a single column or multiple columns of a given table. If an index is defined on a single column of a table, the in... 2016-11-15, 2646🔥, 0💬

Requirements for SQL*Plus Connection in Oracle
What Information Is Needed to Connect SQL*Plus an Oracle Server in Oracle? If you want to connect your SQL*Plus session to an Oracle server, you need to know the following information about this server: The network hostname, or IP address, of the Oracle server. The network port number where the Orac... 2020-08-25, 2643🔥, 0💬

Requirements for Using MySQL in PHP in MySQL
What Do You Need to Connect PHP to MySQL in MySQL? If you want to access MySQL database server in your PHP script, you need to make sure that a MySQL API module (extension) is installed and turned on in your PHP engine. PHP 5 now supports two MySQL API extensions: mysql - This is the standard MySQL ... 2017-07-30, 2639🔥, 0💬

Introduction to Command-Line SQL*Plus Client Tool
Where to find answers to frequently asked questions on Command-Line SQL*Plus Client Tool? I want to learn simple ways to run commands on Oracle database server. Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Command-Line SQL*Plus Client Tool. Cle... 2020-08-25, 2638🔥, 0💬

Calculating the Difference between Two Time Values in MySQL
How To Calculate the Difference between Two Time Values in MySQL? If you have two time values, and you want to know the time difference between them, you can use the TIMEDIFF(time1, time2) function as shown below: SELECT TIMEDIFF(TIME('19:26:50'), TIME('09:26:50')) FROM DUAL; 10:00:00 SELECT TIMEDIF... 2017-12-26, 2626🔥, 0💬

Generate Query Output in HTML Format in Oracle
How To Generate Query Output in HTML Format in Oracle? If you want your query output to be generated in HTML format, you can use the "SET MARKUP HTML ON" to turn on the HTML feature. The following tutorial exercise gives you a good example: SQL&gt; connect HR/retneciyf SQL&gt; SET MARKUP HTM... 2020-07-15, 2605🔥, 0💬

What Is a Database Table in Oracle
What Is a Database Table in Oracle? A database table is a basic unit of data logical storage in an Oracle database. Data is stored in rows and columns. You define a table with a table name, such as employees, and a set of columns. You give each column a column name, such as employee_id, last_name, a... 2020-11-22, 2604🔥, 0💬

Connect SQL*Plus Session to Oracle Server in Oracle
How To Connect a SQL*Plus Session to an Oracle Server in Oracle? In order to connect a SQL*Plus session to an Oracle server, you need to: 1. Obtain the connection information from the Oracle server DBA. 2. Define a new "connect identifier" called "FYI_XE" in your tnsnames.org file with the given con... 2020-08-13, 2602🔥, 0💬

Converting Binary Strings into Unicode Character Strings in SQL Server
Can Binary Strings Be Converted into Unicode Character Strings in SQL Server Transact-SQL? Can binary strings be converted into Unicode character strings? The answer is yes. But you need to know how Unicode characters are represented in a binary format. Remember the following simple rules: An ASCII ... 2017-02-28, 2598🔥, 0💬

Export Data to a CSV File in Oracle
How To Export Data to a CSV File in Oracle? If you want to export data from a table to a file in CSV format, you can use the following steps: Right-click the table name, EMPLOYEES, in the object tree view. Select Export. Select CSV. The Export Data window shows up. Click Format tab. Select Format as... 2019-01-26, 2595🔥, 0💬

Show All Data Files in the Current Database in Oracle
How To View Data Files in the Current Database in Oracle? If you want to get a list of all tablespaces used in the current database instance, you can use the DBA_TABLESPACES view as shown in the following SQL script example: SQL&gt; connect SYSTEM/fyicenter Connected. SQL&gt; col tablespace_... 2019-04-13, 2594🔥, 0💬

Drop a Stored Function in Oracle
How To Drop a Stored Function in Oracle? If there is an existing stored function and you don't want it any more, you can remove it from the database by using the DROP FUNCTION statement as shown in the following script example: SQL&gt; CREATE OR REPLACE FUNCTION GET_SITE 2 RETURN VARCHAR2 AS 3 B... 2018-10-26, 2576🔥, 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, 2576🔥, 0💬

Introduction to Oracle Database 10g Express Edition
Where to find answers to frequently asked questions on Oracle Database 10g Express Edition? I want to learn how to install Oracle database. Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Oracle Database 10g Express Edition with installation instr... 2020-05-15, 2572🔥, 0💬

Measuring Performance of INSERT Statements in SQL Server
How To Measure Performance of INSERT Statements in SQL Server? When indexes are defined for a table, each time a new row is inserted to the table, all the indexes must be updated. This extra update work could slow down the insert statement. To find out how much slower the INSERT statements will be o... 2016-11-13, 2570🔥, 0💬

CREATE VIEW - Creating a View on an Existing Table in SQL Server
How To Create a View on an Existing Table in SQL Server? If you want to a view on an existing table, you can use the CREATE VIEW statement in a simple syntax: CREATE VIEW view_name AS SELECT ... The tutorial exercise below shows you how to create a view to represent sub set of data stored in fyi_lin... 2016-11-05, 2566🔥, 0💬

Using User Defined Functions in SQL Server Transact-SQL
Where to find answers to frequently asked questions on Using User Defined Functions in SQL Server Transact-SQL? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Using User Defined Functions in SQL Server Transact-SQL. Clear answers are provided wit... 2016-12-28, 2559🔥, 0💬

What Is a Table Index in Oracle
What Is a Table Index in Oracle? Index is an optional structure associated with a table that allow SQL statements to execute more quickly against a table. Just as the index in this manual helps you locate information faster than if there were no index, an Oracle Database index provides a faster acce... 2020-11-22, 2555🔥, 0💬

Error: Could not Resolve the Connect Identifier in Oracle
What Happens If You Use a Wrong Connect Identifier in Oracle? Of course, you will get an error, if you use a wrong connect identifier. Here is an example of how SQL*Plus react to a wrong connect identifier: SQL&gt; CONNECT fyi/retneciyf@WRONG; ERROR: ORA-12154: TNS:could not resolve the connect ... 2020-08-13, 2554🔥, 0💬

Escape Special Characters in MySQL
How To Escape Special Characters in SQL statements in MySQL? There are a number of special characters that needs to be escaped (protected), if you want to include them in a character string. Here are some basic character escaping rules: The escape character (\) needs to be escaped as (\\). The singl... 2018-04-12, 2536🔥, 0💬

Use "IN OUT" Parameters in Oracle
How To Use "IN OUT" Parameter Properly in Oracle? Here are the rules about IN OUT parameters: A formal IN OUT parameter acts like an initialized variable. An actual IN OUT parameter must be a variable. An actual IN OUT parameter passes a copy of its value to the formal parameter when entering the pr... 2018-10-19, 2529🔥, 0💬

What Is a User Role in Oracle
What Is a User Role in Oracle? A user role is a group of privileges. Privileges are assigned to users through user roles. You create new roles, grant privileges to the roles, and then grant roles to users.   ⇒ What Is a Database Schema in Oracle ⇐ Relations of a User Account and a Schema in Oracle ... 2020-11-22, 2522🔥, 0💬

What Is Microsoft SQL Server in SQL Server
What is Microsoft SQL Server in SQL Server? Microsoft SQL Server is a relational database management system (RDBMS) developed by Microsoft. It runs on Windows systems and uses Transact-SQL as the query language. Microsoft SQL Server release history: 1993 - SQL Server 4.21 for Windows NT 1995 - SQL S... 2016-12-08, 2520🔥, 0💬

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General MySQL Oracle SQL Server