General MySQL Oracle SQL Server

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Types of Table Joins in MySQL
How To Join Two Tables in a Single Query in MySQL? 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 fir... 2017-12-31, 2933🔥, 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, 2924🔥, 0💬

Entering Microseconds in SQL Statements in MySQL
How To Enter Microseconds in SQL Statements in MySQL? If you want to enter microseconds in a SQL statements, you can enter them right after the time string as a 6-digit number delimited with '.'. '0' will be padded to right if not enough digits. Here are some good examples: SELECT TIME('1997/01/31 0... 2017-12-26, 2923🔥, 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, 2918🔥, 0💬

Start a New Transaction Explicitly in MySQL
How To Start a New Transaction Explicitly in MySQL? If you are confused on the implicit new transaction rules, you can always start a new transaction with the "START TRANSACTION" command to start a new transaction explicitly. "START TRANSACTION" command works in both "Autocommit On" and "Autocommit ... 2016-10-17, 2918🔥, 0💬

SESSION_USER() - Synonym for USER()
What's the difference between SESSION_USER() and USER() functions? SESSION_USER() is a synonym for the USER() function. Related MySQL functions: USER() - Login Name of Current User SESSION_USER() - Synonym for USER() SYSTEM_USER() - Synonym for USER() CURRENT_USER() - Authentication Name of Current ... 2025-01-07, 2902🔥, 0💬

Deleting a User Account in MySQL
How To Delete a User Account in MySQL? If you want to delete a user account, you can connect to the server as "root" and use the "DROP USER ..." command to delete a user account. The tutorial exercise below shows you a good example: &gt;cd \mysql\bin &gt;mysql -u root -pretneciyf mysql mysql... 2017-12-13, 2885🔥, 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, 2885🔥, 0💬

FORMAT_PICO_TIME() - Formatting Picoseconds in Readable Units
How to format a number of picoseconds in a human-readable unit using the FORMAT_PICO_TIME() function? FORMAT_PICO_TIME(con) is a MySQL built-in function that converts a number of picoseconds in a human-readable unit of ps, ns, ms, s, min, h, or d. For example: SELECT FORMAT_PICO_TIME(9), FORMAT_PICO... 2025-09-24, 2869🔥, 0💬

What Is Transaction in MySQL
What Is Transaction in MySQL? A transaction is a logical unit of work requested by a user to be applied to the database objects. MySQL server introduces the transaction concept to allow users to group one or more SQL statements into a single transaction, so that the effects of all the SQL statements... 2016-10-16, 2858🔥, 0💬

Creating a New Database in MySQL
How To Create a New Database in MySQL? A database in a MySQL server is a logical container used to group tables and other data objects together as a unit. If you are the administrator of the server, you can create a new databases using the CREATE DATABASE statements with MySQL client interface progr... 2017-11-11, 2857🔥, 0💬

Inserting Rows with a SELECT Statement in MySQL
How To Insert Multiple Rows with a SELECT Statement in MySQL? If want to insert rows into a table based on data rows from other tables, you can use a sub-query inside the INSERT statement as shown in the following script example: &lt;?php include "mysql_connection.php"; $sql = "INSERT INTO fyi_l... 2017-09-20, 2783🔥, 0💬

Running MySQL Server on a Specific Port in MySQL
How To Run MySQL Server on a Different Port in MySQL? By default, MySQL will listen at port number 3306 for any client connections. But you can change this by starting the server with "--port=portNumber" option. The tutorial exercise shows you how to start the server to listen to a different port nu... 2017-11-29, 2771🔥, 0💬

CRC32() - Cyclic Redundancy Check 32-Bit
How to calculate the 32-bit CRC (Cyclic Redundancy Check) value using the CRC32() function? CRC32(str) is a MySQL built-in function that calculates the 32-bit CRC (Cyclic Redundancy Check) value of a given character string and returns it as an integer. For example: SELECT CRC32('MySQL'), HEX(CRC32('... 2024-07-15, 2753🔥, 0💬

DENSE_RANK() - Density Rank of Sorted Values
How to calculate the density rank of the sorting field expression in the current result set window using the DENSE_RANK() function? DENSE_RANK() is a MySQL built-in window function that calculates the density rank of the sorting field expression in the current result set window. For example: SELECT ... 2024-09-28, 2599🔥, 0💬

JSON_STORAGE_FREE() - Free Space in JSON Value
How to obtain the free space size in a JSON table column using the JSON_STORAGE_FREE() function? JSON_STORAGE_FREE(json) is a MySQL built-in function that returns the free space size in a JSON table column. Free space occurs when JSON table column is partially updated with less data. For example: CR... 2024-12-18, 2597🔥, 0💬

MySQL Functions on Character String Values
Where to find reference information and tutorials on MySQL database functions on string values? I want to know how to use SUBSTRING(), REPLACE() and other character string related functions. Here is a collection of reference information and tutorials on MySQL database functions on string values comp... 2023-11-10, 2585🔥, 0💬

MySQL Functions on System Information
Where to find reference information and tutorials on MySQL database functions on System Information? I want to know how to use DATABASE(), VERSION() and other functions. Here is a collection of reference information and tutorials on MySQL database functions on System Information compiled by FYIcente... 2024-07-15, 2547🔥, 0💬

JSON_QUOTE() - Quoting JSON String
How to convert a regular character string into a JSON (JavaScript Object Notation) string using the JSON_QUOTE() function? JSON_QUOTE(str) is a MySQL built-in function that converts a regular character string into a JSON string by quoting the string with double quotes. It replaces the double-quote c... 2023-12-10, 2531🔥, 0💬

UNCOMPRESSED_LENGTH() - Uncompressed Data Length
How to calculate the original data length of a compressed byte string using the UNCOMPRESSED_LENGTH() function? UNCOMPRESSED_LENGTH(str) is a MySQL built-in function that returns the original data length of a given compressed byte string. For example: SET @bin = x'37000000789C738BF44C4ECD2B49 2DD24BC... 2024-12-18, 2511🔥, 0💬

LAG() - N-Row before Current Row within Window
How to evaluate a field expression on n-row before the current row in the current result set window using the LAG() function? LAG(exp, n, default) is a MySQL built-in window function that evaluates a field expression on n-row before the current row in the current result set window. For example: SELE... 2024-09-28, 2511🔥, 0💬

JSON_TABLE() - Inline Table with JSON Array
How to create an inline table with a JSON Array using the JSON_TABLE() function? JSON_TABLE(json, path COLUMNS (column_list) AS alias) is a MySQL built-in function that creates an inline table by parsing JSON array members. For example: the following statement creates a 1-column table with string me... 2024-11-23, 2491🔥, 0💬

FIRST_VALUE() - First Value of Result Set Window
How to obtain the first value of a field expression in the current result set window using the FIRST_VALUE() function? FIRST_VALUE(exp) is a MySQL built-in window function that returns the first value of a field expression in the current result set window. For example: SELECT help_topic_id AS tip, h... 2024-09-28, 2447🔥, 0💬

COLLATION() - Detecting Character Collation Name
How to detect the character collation name associated to a given character string using the COLLATION() function? COLLATION(str) is a MySQL built-in function that returns the character collation name associated to a given character string. A character collation name refers to a set of rules to sort ... 2025-10-14, 2382🔥, 0💬

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General MySQL Oracle SQL Server