General MySQL Oracle SQL Server

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"CREATE TRIGGER" - Creating a DML Trigger in SQL Server
How To Create a DML Trigger using CREATE TRIGGER Statements in SQL Server? A DML trigger is a trigger declared to handle a DML event, which occurs when an INSERT, UPDATE or DELETE statement is executed. If you want to create a DML trigger, you should use the "CREATE TRIGGER" statement in the followi... 2016-10-25, 2726🔥, 0💬

Violation of Unique Value Constraint in MySQL
What Happens If Unique Value Constraints Are Violated in MySQL? If you are inserting a new record that has values violating a unique constraint, you will get an error. Note that primary key column has a unique value constraint by default. The following tutorial exercise gives you some good examples:... 2018-01-16, 2725🔥, 0💬

What Is Index in MySQL
What Is Index in MySQL? An index is a single column or multiple columns defined to have values pre-sorted to speed up data retrieval speed.   ⇒ What Is View in MySQL ⇐ What Is Foreign Key in MySQL ⇑ Database Basics and Terminologies in MySQL ⇑⇑ MySQL Database Tutorials 2017-07-07, 2725🔥, 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, 2725🔥, 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, 2724🔥, 0💬

Read Consistency in Oracle in Oracle
How Does Oracle Handle Read Consistency in Oracle? Oracle supports two options for you on how to maintain read consistency: READ WRITE (the default option), also called statement-level read consistency. READ ONLY, also called transaction-level read consistency.   ⇒ What Is a READ WRITE Transaction i... 2019-08-23, 2724🔥, 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, 2724🔥, 0💬

Inserting Data into an Existing Table in MySQL
How To Insert Data into an Existing Table in MySQL? If you want to insert a row of data into an existing table, you can use the INSERT INTO statement as shown in the following sample script: &lt;?php include "mysql_connection.php"; $sql = "INSERT INTO fyi_links (id, url) VALUES (" . " 101, 'dev.... 2017-10-08, 2724🔥, 0💬

Deleting All Rows with DELETE Statements in SQL Server
How To Delete All Rows with DELETE Statements in SQL Server? If you want to delete all rows from a table, you have two options: Use the DELETE statement with no WHERE clause. Use the TRUNCATE TABLE statement. Here is an example of deleting all rows with a DELETE statement: SELECT COUNT(*) FROM fyi_l... 2016-10-30, 2723🔥, 0💬

Ways to Join Two Tables in a Single Query in Oracle
How To Join Two Tables in a Single Query in Oracle? Two tables can be joined together in a query in 4 ways: Inner Join: Returns only rows from both tables that satisfy the join condition. Left Outer Join: Returns rows from both tables that satisfy the join condition, and the rest of rows from the fi... 2019-10-27, 2722🔥, 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, 2722🔥, 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, 2722🔥, 0💬

Deleting a Table That Is Used by a View in SQL Server
What Happens If You Delete a Table That Is Used by a View in SQL Server? Assuming that you have a table which is used by a view, and you try to delete that table. SQL Server will let you delete the table without any trouble. But that view will become invalid. The tutorial exercise below shows you wh... 2016-11-04, 2721🔥, 0💬

"CREATE SCHEMA" - Creating a New Schema in a Database in SQL Server
How To Create a New Schema in a Database in SQL Server? If you want to create a new schema in an existing database, you can use the "CREATE SCHEMA" statement as shown in the tutorial example below: USE FyiCenterData; GO CREATE SCHEMA fyi; GO Command(s) completed successfully. A new schema called "fy... 2016-10-22, 2721🔥, 0💬

Report View in SQL Developer in Oracle
What Is the Reports View in Oracle SQL Developer in Oracle? The Reports view lets you browse database information that organized by the server as special views. Information can be browsed include: Database parameters Storage information Session information Cursors Data objects User accounts Security... 2018-10-08, 2720🔥, 0💬

DML Commands Supported in MySQL
How Many SQL DML Commands Are Supported by "mysql" in MySQL? There are 4 SQL Data Manipulation Language (DML) commands that are supported by "mysql". They are listed below with short descriptions: "INSERT INTO tableName ..." - Inserts new data rows into the specified table. "DELETE FROM tableName ..... 2018-02-08, 2719🔥, 0💬

What Is Commit in MySQL
What Is Commit in MySQL? Commit is a way to terminate a transaction with all database changes to be saved permanently to the database server.   ⇒ What Is RollBack in MySQL ⇐ What Is Transaction in MySQL ⇑ Database Basics and Terminologies in MySQL ⇑⇑ MySQL Database Tutorials 2016-10-16, 2718🔥, 0💬

ROLES_GRAPHML() - User Role Graph in GraphML Format
How to obtain User Role Graph in GraphML Format using the ROLES_GRAPHML() function? ROLES_GRAPHML() is a MySQL built-in function that returns user role graph in GraphML format. For example: SELECT ROLES_GRAPHML(); -- +----------------------------- ------------------------------ ---------+-- | ROLES_G... 2025-02-16, 2716🔥, 0💬

Define the ID Column as Auto-Incremented in MySQL
How To Define the ID Column as Auto-Incremented in MySQL? Many tables require an ID column to assign a unique ID number for each row in the table. For example, if you have a table to hold forum member profiles, you need an ID number to identify each member. To allow MySQL server to automatically ass... 2017-09-12, 2715🔥, 0💬

"INSTEAD OF" - Overriding DML Statements with Triggers in SQL Server
How To Override DML Statements with Triggers in SQL Server? Sometime, you may want to implement some business logics in a DML trigger to cancel the DML statement. For example, you may want to check the new email address format provided by the UPDATE statement. If the email address is invalid, you to... 2016-10-22, 2715🔥, 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, 2714🔥, 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, 2714🔥, 0💬

What Are Group Functions in Oracle
What Are Group Functions in Oracle? Group functions are functions applied to a group of rows. Examples of group functions are: COUNT(*) - Returns the number of rows in the group. MIN(exp) - Returns the minimum value of the expression evaluated on each row of the group. MAX(exp) - Returns the maximum... 2019-12-19, 2710🔥, 0💬

Create a Stored Procedure Interactively in Oracle
How To Create a Procedure Interactively in Oracle? If you want to create a stored procedure interactively, you can use the following steps: Open you connection name, like Local_XE. Right-click Procedures. Select Create PROCEDURE. The Create Procedure window shows up. Enter Name as: Hello Click OK. T... 2019-01-12, 2710🔥, 0💬

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General MySQL Oracle SQL Server