General MySQL Oracle SQL Server

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Experiments of Data Locks in Oracle
How To Experiment a Data Lock in Oracle? If you want to have some experience with data locks, you can create two windows running two SQL*Plus sessions. In session 1, you can run a UPDATE statements to create a data lock. Before committing session 2, switch to session 2, and run a UPDATE statements o... 2019-08-08, 2726🔥, 0💬

Turn on Error Logs in MySQL
How To Turn on Error Logs in MySQL? If you want MySQL to write critical errors into a log file, you can use the "--log-error=fileName" option at the "mysqld" command line. The tutorial exercise below shows you a good example on how to use this option: &gt;cd \mysql\bin &gt;mkdir \mysql\logs ... 2017-11-29, 2726🔥, 0💬

Quoting Date and Time Values in MySQL
How To Quote Date and Time Values in SQL Statements in MySQL? If you want to provide date and time values in a SQL statement, you should write them in the format of "yyyy-mm-dd hh:mm:ss", and quoted with single quotes ('). The tutorial exercise below shows you two INSERT statements. The first one us... 2017-06-23, 2725🔥, 0💬

Use an Explicit Cursor without OPEN Statements in Oracle
How To Use an Explicit Cursor without OPEN Statements in Oracle? If you want to open a cursor and loop through its data rows in quick way, you can use the FOR ... IN ... LOOP statement in the same way as the implicit cursor. The following tutorial exercise gives you a good example: CREATE OR REPLACE... 2018-04-07, 2722🔥, 0💬

Show the Current Transaction Mode in MySQL
How To Find Out the Current Transaction Mode in MySQL? If you are not sure about your current transaction mode, you can use the "SELECT @@AUTOCOMMIT FROM DUAL" statement to find out as shown in the following tutorial exercise: &gt;\mysql\bin\mysql -u dev -piyf fyi mysql&gt; SELECT @@AUTOCOMM... 2016-10-17, 2722🔥, 0💬

What Is a Subquery in MySQL
What Is a Subquery in MySQL? A subquery is a SELECT statement used as part of the selection criteria of the main SELECT statement. The subquery specified in the WHERE clause will be evaluated repeated on each row of the selection base table. The output of the subquery will be used in the final evalu... 2017-09-17, 2721🔥, 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, 2720🔥, 0💬

Transaction Commit When Session Ended in Oracle
What Happens to the Current Transaction If the Session Is Ended in Oracle? If a session is ended, the current transaction in that session will be committed and ended. All the database changes made in the current transaction will become permanent. This is called an implicit commit when session is end... 2019-08-23, 2719🔥, 0💬

Attributes of the Implicit Cursor in Oracle
How To Use Attributes of the Implicit Cursor in Oracle? Right after executing a DML statement, you retrieve any attribute of the implicit cursor by using SQL%attribute_name, as shown in the following tutorial exercise: CREATE TABLE student (id NUMBER(5) PRIMARY KEY, first_name VARCHAR(80) NOT NULL, ... 2018-02-01, 2719🔥, 0💬

Drop an Existing Index in Oracle
How To Drop an Existing Index in Oracle? If you don't need an existing index any more, you should delete it with the DROP INDEX statement. Here is an example SQL script: CREATE TABLE student (id NUMBER(5) PRIMARY KEY, first_name VARCHAR(80) NOT NULL, last_name VARCHAR(80) NOT NULL, birth_date DATE N... 2020-02-20, 2718🔥, 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, 2715🔥, 0💬

Defining and Using Table Alias Names in SQL Server
How To Define and Use Table Alias Names in SQL Server? When column names need to be prefixed with table names, you can define table alias name and use them to prefix column names. To define an alias for a table name, just enter the alias name right after the original table name in the FROM clause as... 2016-10-30, 2715🔥, 0💬

in Oracle
How To Delete All Rows from a Table in Oracle? 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. The TRUNCATE statement is more efficient the DELETE statement. The tutorial exercise shows you a good exa... 2020-01-04, 2713🔥, 0💬

Date-Only DATETIME Values in SQL Server Transact-SQL
What Happens If Date-Only Values Are Provided for DATETIME in SQL Server Transact-SQL? If only date value is provided in a DATETIME variable, the SQL Server will pad the time value with a zero, or '00:00:00.000', representing the midnight time of the day. The tutorial exercise below gives you some g... 2017-04-08, 2713🔥, 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, 2711🔥, 0💬

ALTER VIEW - Modifying Existing Views in SQL Server
How To Modify the Underlying Query of an Existing View in SQL Server? If you have an existing view, and want to change the underlying SELECT statement, you can use the "ALTER VIEW ..." statement to redefine the view. The tutorial exercise below shows you how modify an existing view: USE FyiCenterDat... 2016-11-04, 2711🔥, 0💬

Use DML Statements in PL/SQL in Oracle
Can DML Statements Be Used in PL/SQL in Oracle? Yes, you can run almost any DML statements in PL/SQL directly. To manipulate Oracle database data you can include INSERT, UPDATE, and DELETE statements, directly in PL/SQL programs, without any special notation, as shown in the following sample code: (... 2018-10-13, 2710🔥, 0💬

Export Data with Field Delimiters in Oracle
How To Export Data with a Field Delimiter in Oracle? The previous exercise allows you to export data with fixed field lengths. If you want export data with variable field lengths and field delimiters, you can concatenate your fields with an expression in the SELECT clause as shown in the tutorial ex... 2018-06-27, 2710🔥, 0💬

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, 2710🔥, 0💬

Experiment with Data Locks in MySQL
How To Experiment Data Locks in MySQL? If you want to have some experience with data locks, you can create two windows running two mysql transactions in two sessions. In session 1, you can run a UPDATE statement with REPEATABLE READ transaction isolation level to create an exclusive lock. Before com... 2017-04-28, 2709🔥, 0💬

Enabling TCP/IP Protocol on a SQL Server
How To Enable TCP/IP Protocol on a SQL Server? By default, the TCP/IP protocol is turned off when a SQL Server is installed to reduce security risk. But if you want applications to connect and access the SQL Server, you need to enable the TCP/IP protocol on the server by following this tutorial: 1. ... 2024-07-25, 2707🔥, 0💬

Giving Privileges at Server Level in MySQL
How To Grant User Privileges at the Global Level in MySQL? If you want to grant a user privilege at the global level, you can use the "GRANT privilegeName ON *.* TO userName" command. The argument "*.*" in the command stands for all database and all tables. The following tutorial exercise shows you ... 2017-08-21, 2707🔥, 0💬

Types of Cursors Supported in PL/SQL in Oracle
How Many Types of Cursors Supported in PL/SQL in Oracle? PL/SQL supports two types of cursors: The implicit cursor - A single default cursor that automatically connects to the last DML statement executed. Explicit cursors - User defined cursors with specific DML statements and execution statuses.   ... 2018-02-01, 2706🔥, 0💬

Tables Using InnoDB Storage Engine in MySQL
How To Create a New Table Using the InnoDB Storage Engine in MySQL? InnoDB storage engine was developed by Innobase Oy, which is an Oracle company now. InnoDB is transaction safe, and has been used by a number of large Websites, like Slashdot.org. InnoDB is not the default storage engine. You need t... 2017-09-01, 2706🔥, 0💬

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General MySQL Oracle SQL Server