General MySQL Oracle SQL Server

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SELECT Statements with JOIN and Subqueries in MySQL
Where to find answers to frequently asked questions on SELECT Statements with JOIN and Subqueries in MySQL? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on SELECT Statements with JOIN and Subqueries in MySQL. Clear answers are provided with tutori... 2017-12-31, 2430🔥, 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, 2430🔥, 0💬

Testing Table for SELECT Statements in SQL Server
How To Create a Testing Table with Test Data to try with SELECT statements in SQL Server? If you want to follow the tutorial exercises presented in this collection, you need to create a testing table and insert some test data, as shown in the following sample script: CREATE TABLE fyi_links (id INTEG... 2016-10-26, 2430🔥, 0💬

Drop an Existing View in MySQL
How To Drop an Existing View in MySQL? If you have an existing view, and you don't want it anymore, you can delete it by using the "DROP VIEW viewName" statement as shown in the following script: mysql&gt; DROP VIEW faqComment; Query OK, 0 rows affected (0.00 sec) mysql&gt; SELECT * FROM faq... 2018-01-24, 2429🔥, 0💬

System Databases Used by SQL Servers in SQL Server
What are system databases in SQL Server? System databases are created by the SQL Server itself during the installation process. System databases are used by the SQL server to help manage other user databases and client execution sessions. SQL Server 2005 Express Edition uses 4 system databases: mast... 2016-11-20, 2429🔥, 0💬

What Is a Procedure in Oracle
What Is a Procedure in Oracle? A procedure is a named program unit. It consists of three parts: Declaration Part - Defining the procedure name, calling parameters, local variables and local procedures. Declaration part is required. Execution Part - Defining execution logic with executable statements... 2018-01-27, 2426🔥, 0💬

Experiment with Dead Locks in MySQL
How To Experiment Dead Locks in MySQL? If you want to have some experience with dead locks, you can create two windows running two mysql transactions in two sessions at the REPEATABLE READ transaction isolation level. Then run some UPDATE statements as shown in the tutorial exercise below: (session ... 2017-07-21, 2425🔥, 0💬

Define a Variable to Match Column Data Type in Oracle
How To Define a Variable to Match a Table Column Data Type in Oracle? If you have a table, and want to define some variables to have exactly the same data types as some columns in that table, you can use table_name.column_name%TYPE as data types to define those variables. The tutorial sample below s... 2018-08-14, 2424🔥, 0💬

Using Regular Expression with REGEXP in MySQL
How To Use Regular Expression in Pattern Match Conditions in MySQL? If you have a pattern that is too complex for LIKE to handle, you can use the regular expression pattern condition: REGEXP. The following tutorial exercise provides you some good examples: SELECT 'FYICenter.com' REGEXP '.*fyi.*' FRO... 2018-03-24, 2424🔥, 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, 2423🔥, 0💬

Creating a Test Table in MySQL
How To Create a Testing Table in MySQL? If you want to practice DML statements, like INSERT, UPDATE and DELETE, you should create a testing table. The tutorial exercise shows you a good example: mysql&gt; CREATE TABLE fyi_links (id INTEGER PRIMARY KEY, url VARCHAR(80) NOT NULL, notes VARCHAR(102... 2018-01-24, 2423🔥, 0💬

Converting Numeric Expressions from One Data Type to Another in SQL Server
How To Convert a Numeric Expression from One Data Type to Another in SQL Server Transact-SQL? There are 4 ways to convert a numeric expression from one data type to another data type: Implicit conversion by arithmetic operations - When arithmetic operations are performed on expressions of different ... 2017-03-27, 2423🔥, 0💬

Count Duplicated Values in a Column in Oracle
How To Count Duplicated Values in a Column in Oracle? If you have a column with duplicated values, and you want to know what are those duplicated values are and how many duplicates are there for each of those values, you can use the GROUP BY ... HAVING clause as shown in the following example. It re... 2019-11-21, 2422🔥, 0💬

Working with NULL Values in SQL Server Transact-SQL
Where to find answers to frequently asked questions on Working with NULL Values in SQL Server Transact-SQL? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Working with NULL Values in SQL Server Transact-SQL. Clear explanations and tutorial exerci... 2017-02-08, 2420🔥, 0💬

Run Queries on External Tables in Oracle
How To Run Queries on External Tables in Oracle? If you have an external table defined as a text file with the ORACLE_LOADER driver, you can add data to the text file, and query the text file through the external table. By default, data fields in the text file should be terminated by ','. The tutori... 2016-10-15, 2420🔥, 0💬

PHP ODBC - odbc_fetch_array() - Looping through Returning Rows
PHP ODBC - How To Loop through Returning Rows? The best way to query tables and loop through returning rows is to run a SELECT statement with the odbc_exec() function, catch the returning object as a result set, and loop through the result with odbc_fetch_array() function in a while loop as shown in... 2024-05-29, 2419🔥, 0💬

Major Storage Engines Supported in MySQL in MySQL
What Are Storage Engines in MySQL? Storage engines are programs that are integrated into MySQL database management system to manage data tables. MySQL 5.0 supports the following major storage engines: MyISAM Storage Engine - MySQL default storage engine. Based on ISAM database concept. MyISAM is not... 2017-09-12, 2419🔥, 0💬

Transaction Committed when DDL Statement Executed in MySQL
What Happens to the Current Transaction If a DDL Statement Is Executed in MySQL? If a DDL statement is executed, the current transaction will be committed and ended. All the database changes made in the current transaction will become permanent. This is called an implicit commit by a DDL statement. ... 2016-10-17, 2419🔥, 0💬

Create a Test Table for DML Testing in Oracle
How To Create a Testing Table in Oracle? If you want to practice DML statements, you should create a testing table as shown in the script below: CREATE TABLE fyi_links (id NUMBER(4) PRIMARY KEY, url VARCHAR2(80) NOT NULL, notes VARCHAR2(1024), counts NUMBER, created DATE DEFAULT (sysdate)); Table cr... 2020-02-07, 2414🔥, 0💬

Turn On and Off Recycle Bin for the Instance in Oracle
How To Turn On or Off Recycle Bin for the Instance in Oracle? You can turn on or off the recycle bin feature for an instance in the instance parameter file with "recyclebin=on/off". You can also turn on or off the recycle bin feature on the running instance with a SQL*Plus command, if you log in as ... 2019-05-14, 2414🔥, 0💬

Index Speeding Up SELECT Statements in SQL Server
Does Index Speed Up SELECT Statements in SQL Server? If you want to see the impact of indexes on SELECT statements, you can run the same SELECT statement on "fyi_links" and "fyi_links_indexed" tables. See the tutorial exercise below: USE FyiCenterData; GO -- Run SELECT on the table without indexes D... 2016-11-13, 2414🔥, 0💬

Define an Explicit Cursor in Oracle
How To Define an Explicit Cursor in Oracle? An explicit cursor must be defined in the declaration part of a procedure or function with the CURSOR ... IS statement as shown in the following sample script: DECLARE CURSOR c_list IS SELECT * FROM countries; CURSOR t_list IS SELECT * FROM employees WHERE... 2018-07-22, 2413🔥, 0💬

Pass a Parameter to a Cursor in Oracle
How To Pass a Parameter to a Cursor in Oracle? When you define a cursor, you can set a formal parameter in the cursor. The formal parameter will be replaced by an actual parameter in the OPEN cursor statement. Here is a good example of a cursor with two parameters: CREATE OR REPLACE PROCEDURE FYI_CE... 2018-07-18, 2413🔥, 0💬

Viewing Log File with "mysqlbinlog" in MySQL
How To Use mysqlbinlog to View Binary Logs in MySQL? If you have binary logs turned on, you can use "mysqlbinlog" to view the binary log files. The tutorial exercise below shows you how to view two binary files together: &gt;cd \mysql\bin &gt;mysql -u root -pretneciyf test &gt;mysqlbinlo... 2017-11-29, 2413🔥, 0💬

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General MySQL Oracle SQL Server