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Rename an Existing Column in a Table in MySQL
How To Rename an Existing Column in a Table in MySQL? If you have an existing column in a table and you want to change the column name, you can use the "ALTER TABLE ... CHANGE" statement. This statement allows you to change the name of a column, and its definition. The tutorial script below gives yo...
2018-03-04, 668👍, 0💬

Transaction Waiting for a Data Lock in MySQL
How Long a Transaction Will Wait for a Data Lock in MySQL? If you issue a UPDATE or DELETE statement on a row that has an exclusive lock owned by another session, your statement will be blocked to wait for the other session to release the lock. But the wait will be timed out after the predefined inn...
2017-04-28, 667👍, 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, 664👍, 0💬

Difference between CHAR and VARCHAR in MySQL
What Are the Differences between CHAR and VARCHAR in MySQL? CHAR and VARCHAR are both ASCII character data types by default. But they have the following major differences: CHAR stores values in fixed lengths. Values are padded with space characters to match the specified length. VARCHAR stores value...
2018-01-19, 663👍, 0💬

Date and Time Data Types in MySQL
What Are Date and Time Data Types in MySQL? MySQL supports the following date and time data types: DATE - A date in the range of '1000-01-01' and '9999-12-31'. Default DATE format is "YYYY-MM-DD". DATETIME - A date with the time of day in the range of '1000-01-01 00:00:00' and '9999-12-31 23:59:59'....
2018-01-19, 662👍, 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.   ⇒Database Basics and Terminologies in MySQL ⇒⇒MySQL Database Tutorials
2017-07-07, 662👍, 0💬

Difference between BINARY and VARBINARY in MySQL
What Are the Differences between BINARY and VARBINARY in MySQL? Both BINARY and VARBINARY are both binary byte data types. But they have the following major differences: BINARY stores values in fixed lengths. Values are padded with 0x00. VARBINARY stores values in variable lengths. Values are not pa...
2018-01-19, 661👍, 0💬

Retrieving the Last Sequence ID in MySQL
How To Get the Last ID Assigned by MySQL in MySQL? If you use an ID column with AUTO_INCREMENT attribute, you can use the mysql_insert_id() function to get the last ID value assigned by the MySQL server, as shown in the sample script below: &lt;?php include "mysql_connection.php"; $sql = "INSERT...
2017-09-12, 661👍, 0💬

Creating a Test Table in MySQL Server in MySQL
How To Create a Test Table in Your MySQL Server in MySQL? If you want to create a test table in your MySQL server, you can use the "mysql" program in a command window as shown in the following tutorial: &gt;cd \mysql\bin &gt;mysql -u root Welcome to the MySQL monitor. Commands end with ; or ...
2018-06-06, 659👍, 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, 659👍, 0💬

What Is a Data Lock in MySQL
What Is a Data Lock in MySQL? MySQL uses two types of data locks at two levels to provide you the transaction isolation level you need: Share Lock at Row Level (S) - A data row is locked by a transaction for reading. Exclusive Lock at Row Level (X) - A data row is locked by a transaction for updatin...
2017-04-28, 658👍, 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, 657👍, 0💬

Command-Line End User Interface 'mysql'
Where to find answers to frequently asked questions on Command-Line End User Interface "mysql"? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Command-Line End User Interface "mysql". Clear answers are provided with tutorial exercises on mysql co...
2018-04-28, 656👍, 0💬

Creating New Tables with SELECT Statements in MySQL
How To Create a New Table by Selecting Rows from Another Table in MySQL? Let's say you have a table with many data rows, now you want to create a backup copy of this table of all rows or a subset of them, you can use the "CREATE TABLE ... SELECT" statement. The tutorial script below gives you a good...
2018-03-04, 656👍, 0💬

What Is MyISAM in MySQL
What Is MyISAM in MySQL? MyISAM is a storage engine used as the default storage engine for MySQL database. MyISAM is based on the ISAM (Indexed Sequential Access Method) concept and offers fast data storage and retrieval. But it is not transaction safe.   ⇒Database Basics and Terminologies in MySQL ...
2017-07-03, 656👍, 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, 655👍, 0💬

Difference between CHAR and NCHAR in MySQL
What Are the Differences between CHAR and NCHAR in MySQL? Both CHAR and NCHAR are fixed length string data types. But they have the following differences: CHAR's full name is CHARACTER. NCHAR's full name is NATIONAL CHARACTER. By default, CHAR uses ASCII character set. So 1 character is always store...
2018-01-19, 655👍, 0💬

UPDATE with Subquery Returning No Rows in MySQL
What Happens If the UPDATE Subquery Returns No Rows in MySQL? If you use a subquery to assign new values in the SET clause in an UPDATE statement, and the subquery returns no rows for an outer row, MySQL will provide a NULL value to the SET clause. The tutorial exercise below shows you a good exampl...
2018-01-08, 655👍, 0💬

Quoting Text Values in MySQL
How To Quote Text Values in SQL Statements in MySQL? Text values in SQL statements should be quoted with single quotes ('). If the text value contains a single quote ('), it should be protected by replacing it with two single quotes (''). In SQL language syntax, two single quotes represents one sing...
2017-06-28, 654👍, 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, 653👍, 0💬

Add a New Column to an Existing Table in MySQL
How To Add a New Column to an Existing Table in MySQL? If you have an existing table with existing data rows, and want to add a new column to that table, you can use the "ALTER TABLE ... ADD COLUMN" statement. The tutorial script below shows you a good example: mysql&gt; ALTER TABLE tip ADD COLU...
2018-03-04, 652👍, 0💬

What Is a Dead Lock in MySQL
What Is a Dead Lock in MySQL? A dead lock is phenomenon happens between two transactions with each of them holding a lock that blocks the other transaction as shown in the following diagram: (transaction 1) (transaction 2) update row X to create lock 1 update row Y to create lock 2 update row X (blo...
2017-04-28, 652👍, 0💬

Verify MySQL Server Status in MySQL
How Do You Know If Your MySQL Server Is Alive in MySQL? If you want to know whether your MySQL server is alive, you can use the "mysqladmin" program in a command window as shown in the following tutorial: &gt;cd \mysql\bin &gt;mysqladmin -u root ping mysqld is alive The "mysqld is alive" mes...
2018-06-06, 651👍, 0💬

What Is "mysqlimport" Command in MySQL
What Is "mysqlimport" in MySQL? "mysqlimport" - A command-line interface for administrators or end users to load data files into tables program tool to load data into tables. Here is a sample commands supported by "mysqlimport": "mysqlimport databaseName fileName" - Imports the data from the specifi...
2018-05-19, 651👍, 0💬

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