General MySQL Oracle SQL Server

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What Is Foreign Key in MySQL
What Is Foreign Key in MySQL? A foreign key is a single column or multiple columns defined to have values that can be mapped to a primary key in another table.   ⇒ What Is Index in MySQL ⇐ What Is Primary key in MySQL ⇑ Database Basics and Terminologies in MySQL ⇑⇑ MySQL Database Tutorials 2017-07-07, 2436🔥, 0💬

Close MySQL Connection Objects in MySQL
How To Close MySQL Connection Objects in MySQL? MySQL connection objects created with mysql_connect() calls should be closed as soon as you have finished all of your database access needs by calling mysql_close($con) function. This will reduce the consumption of connection resources on your MySQL se... 2017-11-11, 2433🔥, 0💬

Retrieving Execution Error Message in MySQL
How To Get MySQL Statement Execution Errors in MySQL? When you execute a MySQL statement with mysql_query(), and the statement failed, mysql_query() will return the Boolean value FALSE. This is good enough to tell that there is something wrong with that statement. But if you want to know more about ... 2017-10-23, 2431🔥, 0💬

Selecting Other User's Database in MySQL
Can You Select Someone Else Database in MySQL? If your MySQL server is provided by an Internet service company, they will provide you one database for your use only. There are many other databases on the server for other users. But your user account will have no privilege to select other databases. ... 2017-10-23, 2431🔥, 0💬

Group Functions with Non-group Selections in MySQL
Can Group Functions Be Mixed with Non-group Selection Fields in MySQL? 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 invalid S... 2017-10-16, 2431🔥, 0💬

Concatenating Character Strings in MySQL
How To Concatenate Two Character Strings in MySQL? If you want concatenate multiple character strings into one, you need to use the CONCAT() function. Here are some good examples: SELECT CONCAT('Welcome',' to') FROM DUAL; Welcome to SELECT CONCAT('FYI','center','.com') FROM DUAL; FYIcenter.com   ⇒ E... 2018-04-07, 2429🔥, 0💬

Number of Rows Selected or Affected in MySQL
How To Get the Number of Rows Selected or Affected by a SQL Statement in MySQL? There are two functions you can use the get the number of rows selected or affected by a SQL statement: mysql_num_rows($res) - Returns the number of rows selected in a result set object returned from SELECT statement. my... 2017-10-08, 2429🔥, 0💬

Counting Duplicated Values in a Column in MySQL
How To Count Duplicated Values in a Column in MySQL? 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 ret... 2017-10-16, 2426🔥, 0💬

List All Tables with "mysql" Command in MySQL
How To Show All Tables with "mysql" in MySQL? If you want to see all the tables in a database, you run the non-SQL command "SHOW TABLES" at the "mysql" prompt. See the following tutorial exercise for example: &gt;cd \mysql\bin &gt;mysql -u root test Welcome to the MySQL monitor. Commands end... 2018-02-28, 2424🔥, 0💬

Data File of BDB Storage Engine in MySQL
Where Table Data Is Stored by the BDB Storage Engine in MySQL? By default, MySQL provides \mysql\data directory for all storage engines to store table data. Under \mysql\data directory, the BDB storage engine will create one file for each table to store table data and index data. If a new table is c... 2017-08-13, 2423🔥, 0💬

Predefined User Accounts in MySQL
What Are the Predefined User Accounts in MySQL? There is only one predefined user account called "root": "root" was created during the installation process. "root" has no password initially. You need to assign a new password as soon as you finishes the installation. "root" has all access privileges ... 2017-09-08, 2419🔥, 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, 2415🔥, 0💬

Query with an Inner Join in MySQL
How To Write a Query with an Inner Join in MySQL? If you want to query from two tables with an inner join, you can use the INNER JOIN ... ON clause in the FROM clause. The tutorial exercise below creates another testing table and returns output with an inner join from two tables: fyi_links and fyi.r... 2017-12-31, 2414🔥, 0💬

Turn on Binary Logs in MySQL
How To Turn on Binary Logs in MySQL? If you want MySQL to write binary logs to a file, you can use the "--log-bin=fileBaseName" 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 &gt... 2017-11-29, 2413🔥, 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, 2412🔥, 0💬

Data Removed in MEMORY Tables in MySQL
What Happens to MEMORY Tables When MySQL Server Is Stopped in MySQL? If you have data rows stored in a table with the MEMORY storage engine, and the MySQL server has been shut down by the DBA, all data rows will be removed. But the table structure will remain in the server. The tutorial exercise bel... 2017-08-08, 2410🔥, 0💬

Delete an Existing Column in a Table in MySQL
How To Delete an Existing Column in a Table in MySQL? If you have an existing column in a table and you do not need that column any more, you can delete it with "ALTER TABLE ... DROP COLUMN" statement. Here is a tutorial script to delete an existing column: mysql&gt; ALTER TABLE tip DROP COLUMN ... 2018-03-04, 2408🔥, 0💬

Entering Boolean Values in MySQL
How To Enter Boolean Values in SQL Statements in MySQL? If you want to enter Boolean values in SQL statements, you use (TRUE), (FALSE), (true), or (false). Here are some good examples: SELECT TRUE, true, FALSE, false FROM DUAL; +------+------+-------+------- +| TRUE | TRUE | FALSE | FALSE | +------+... 2018-03-31, 2403🔥, 0💬

Shutdown MySQL Server Properly in MySQL
How To Properly Shutdown MySQL Server Daemon mysqld in MySQL? The proper way to shutdown your MySQL server is to the use "mysqladmin shutdown" command. Other ways to shutdown your server include: Enter "mysqladmin -u root -ppassowrd shutdown" command with options in a command window. Use Windows Tas... 2017-12-04, 2400🔥, 0💬

CREATE TABLE Statement in MySQL
How To Create a New Table in MySQL? If you want to create a new table, you can use the "CREATE TABLE" statement. The following tutorial script shows you how to create a table called "tip": mysql&gt; CREATE TABLE tip (id INTEGER PRIMARY KEY, subject VARCHAR(80) NOT NULL, description VARCHAR(256) ... 2018-03-10, 2399🔥, 0💬

Commit the Current Transaction in MySQL
How To Commit the Current Transaction in MySQL? If you have used some DML statements updated some data objects, and you want to have the updates to be permanently recorded in the database, you can use the COMMIT command. It will make all the database changes made in the current transaction become pe... 2016-10-17, 2397🔥, 0💬

Retrieving MySQL Server information in MySQL
How To Get Some Basic Information Back from MySQL Servers in MySQL? Once you got a MySQL server connection object successfully, you can use mysql_get_server() and mysql_get_host_info() to get some basic information from your MySQL server. The tutorial exercise below is a good example: &lt;?php $... 2017-11-11, 2395🔥, 0💬

Apply Filtering Criteria at Group Level in MySQL
How To Apply Filtering Criteria at Group Level in MySQL? If you want to return only specific groups from the query, you can apply filtering criteria at the group level by using the HAVING clause inside the GROUP BY clause. Note group functions can also be used in HAVING conditions. The following tut... 2017-10-16, 2394🔥, 0💬

VALIDATE_PASSWORD_STRENGTH() - Password Strength Test
How to test the strength of a password using the VALIDATE_PASSWORD_STRENGTH() function? VALIDATE_PASSWORD_STRENGTH(pas sword)is a MySQL built-in function that calculates the strength of a given password. It requires validate_password plugin component to be installed. For example: SELECT VALIDATE_PAS... 2024-12-18, 2392🔥, 0💬

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General MySQL Oracle SQL Server