General MySQL Oracle SQL Server

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Assign Names to Query Output Columns in MySQL
How To Name Query Output Columns in MySQL? Each column in the query output has a default name. If you don't like the default name, you can specify a new name for any column in the query output by using the AS clause. The following statement shows you a good example: mysql&gt; SELECT tag AS Categ... 2017-09-28, 2588🔥, 0💬

Filerting out Duplications in Returning Rows in MySQL
How To Filter Out Duplications in Returning Rows in MySQL? If there are duplications in the returning rows, and you want to remove the duplications, you can use the keyword DISTINCT in the SELECT clause. The DISTINCT applies to the combination of all data fields specified in the SELECT clause. The t... 2018-01-06, 2576🔥, 0💬

Rename an Existing Table in MySQL
How To Rename an Existing Table in MySQL? If you want to rename an existing table, you can use the "ALTER TABLE ... RENAME TO" statement. The tutorial script below shows you a good example: mysql&gt; ALTER TABLE tip RENAME TO faq; Query OK, 0 rows affected (0.01 sec) mysql&gt; SELECT * FROM ... 2018-02-14, 2567🔥, 0💬

Giving Privileges at the Database Level in MySQL
How To Grant User Privileges at the Database Level in MySQL? If you want to grant a user privilege at the database level, you can use the "GRANT privilegeName ON databaseName.* TO userName" command. The argument "databasename.*" in the command stands for all tables in the specified database. The fol... 2017-08-21, 2567🔥, 0💬

What Is a SELECT Query Statement in MySQL
What Is a SELECT Query Statement in MySQL? The SELECT statement is also called the query statement. It is the most frequently used SQL statement in any database application. A SELECT statement allows you to retrieve data from one or more tables or views, with different selection criteria, grouping c... 2017-11-05, 2565🔥, 0💬

Selecting Columns in a Query in MySQL
How To Select Some Columns from a Table in MySQL? If you want explicitly tell the query to return some columns, you can specify the column names in the SELECT clause. The following select statement returns only two columns, "id" and "url" from the table "fyi_links": mysql&gt; SELECT id, url FROM... 2017-11-05, 2561🔥, 0💬

Adding More Data to the Test Table in MySQL
How To Add More Data to the Testing Table in MySQL? If you want to continue with other tutorial exercises in this FAQ collection, you need to add more data to the testing table. Follow the script below to add a new column and: mysql&gt; ALTER TABLE fyi_links ADD COLUMN tag VARCHAR(8); mysql&... 2017-11-02, 2558🔥, 0💬

Using LIKE Conditions in MySQL
How To Use LIKE Conditions in MySQL? A LIKE condition is also called pattern patch. There are 3 main rules on using LIKE condition: '_' is used in the pattern to match any one character. '%' is used in the pattern to match any zero or more characters. ESCAPE clause is used to provide the escape char... 2018-03-24, 2528🔥, 0💬

Using Group Functions in the ORDER BY Clause in MySQL
Can Group Functions Be Used in the ORDER BY Clause in MySQL? If the query output is aggregated as groups, you can sort the groups by using group functions in the ORDER BY clause. The following statement returns how many links were created in each year in each tag. The group output is sorted by the c... 2017-12-31, 2527🔥, 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, 2505🔥, 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, 2504🔥, 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, 2495🔥, 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, 2481🔥, 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, 2383🔥, 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, 2376🔥, 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, 2305🔥, 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, 2254🔥, 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, 2198🔥, 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, 2183🔥, 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, 2156🔥, 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, 2111🔥, 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, 2057🔥, 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, 2028🔥, 0💬

LAST_VALUE() - Last Value of Result Set Window
How to obtain the last value of a field expression in the current result set window using the LAST_VALUE() function? LAST_VALUE(exp) is a MySQL built-in window function that returns the last value of a field expression in the current result set window. For example: SELECT help_topic_id AS tip, help_... 2024-09-28, 2001🔥, 0💬

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General MySQL Oracle SQL Server