General MySQL Oracle SQL Server

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CURRENT_ROLE() - Current Role of Logged-In User
How to obtain the current role of the logged-in user using the CURRENT_ROLE() function? CURRENT_ROLE() is a MySQL built-in function that returns the current role of the logged-in user. For example: SELECT CURRENT_ROLE(); -- +----------------+ -- | CURRENT_ROLE() | -- +----------------+ -- | NONE | -... 2024-07-15, 2691🔥, 0💬

Updating Values in a Table in MySQL
How To Update Values in a Table in MySQL? If you want to update some values in one row or multiple rows in a table, you can use the UPDATE statement. The tutorial script below shows a good example: mysql&gt; UPDATE fyi_links SET counts = 999, notes = 'Good.' WHERE id = 101; Query OK, 1 row affec... 2018-01-13, 2690🔥, 0💬

Turn on Query Logs in MySQL
How To Turn on Query Logs in MySQL? If you want MySQL to write query logs to a file, you can use the "--log=fileName" option at the "mysqld" command line. The tutorial exercise below shows you a good example on how to use this option and view the query log file: &gt;cd \mysql\bin &gt;mkdir \... 2017-12-04, 2689🔥, 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, 2689🔥, 0💬

Counting Groups Returned from GROUP BY in MySQL
How To Count Groups Returned with the GROUP BY Clause in MySQL? If you use the COUNT(*) function on groups returned with the GROUP BY clause, it will count the number of rows within each group, not the number of groups. If you want to count the number of groups, you can put the GROUP BY query into a... 2017-12-21, 2688🔥, 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, 2688🔥, 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, 2687🔥, 0💬

Returning the Second 5 Rows in MySQL
How To Return the Second 5 Rows in MySQL? If you want to display query output in multiple pages with 5 rows per page, and the visitor wants to see the output for the second page, you need to display query output from row 6 to row 10. You can use the "LIMIT startRow maxRows" clause to return only row... 2017-12-21, 2686🔥, 0💬

Expressions with NULL Values in MySQL
What Happens If NULL Values Are Involved in Expressions in MySQL? If NULL values are used in expressions, the resulting values will be NULL values. In other words: Arithmetic expressions with NULL values result NULL values. Comparison expressions with NULL values result NULL values. Logical expressi... 2018-03-28, 2684🔥, 0💬

What Is a User Account in MySQL
What Is a User Account in MySQL? A user account is identified by a user name and defines the user's attributes, including the following: Password for connection authentication. User privileges, for examples: Shutdown_priv, Create_priv, Drop_priv, Insert_priv, Update_priv, Delete_priv, etc.. Various ... 2017-12-13, 2684🔥, 0💬

Sorting Output in Descending Order in MySQL
How To Sort Output in Descending Order in MySQL? If you want to sort a column in descending order, you can specify the DESC keyword in the ORDER BY clause. The following SELECT statement first sorts the "tag" in descending order, then sorts the "counts" in ascending order: mysql&gt; SELECT tag, ... 2017-11-02, 2684🔥, 0💬

Giving User Read-only Access in MySQL
How To Give a User Read-Only Access to a Database in MySQL? If you want give a user read-only access to a database, you can grant to him/her only the "SELECT" privilege, so that he/she can not run any DDL statements, and any INSERT, UPDATE, or DELETE statements. The tutorial exercise gives you a goo... 2017-08-21, 2684🔥, 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, 2677🔥, 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, 2677🔥, 0💬

Sort by Multiple Columns in MySQL
Can the Query Output Be Sorted by Multiple Columns in MySQL? You can specifying multiple columns in the ORDER BY clause as shown in the following example statement, which returns employees' salaries sorted by department and salary value: mysql&gt; SELECT tag, counts, url, DATE(created) FROM fyi_... 2017-11-02, 2670🔥, 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, 2669🔥, 0💬

Including Comments in SQL Statements in MySQL
How To Include Comments in SQL Statements in MySQL? If you want to include comments in a SQL statement, you can first enter "--", then enter your comment until the end of the line. The tutorial exercise below shows you some good examples: SELECT 'Hello world!' FROM DUAL; -- My first SQL statement! I... 2018-04-12, 2666🔥, 0💬

Drop an Existing Table in MySQL
How To Drop an Existing Table in MySQL? If you want to delete an existing table and its data rows, you can use the "DROP TABLE" statement as shown in the tutorial script below: mysql&gt; SELECT * FROM tipBackup; +----+-------------+---------- ---------------+-------------+| id | subject | descri... 2018-02-14, 2660🔥, 0💬

Server Daemon mysqld Administration in MySQL
Where to find answers to frequently asked questions on Server Daemon mysqld Administration in MySQL? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Server Daemon mysqld Administration in MySQL. Clear answers are provided with tutorial exercises o... 2017-12-09, 2660🔥, 0💬

UNCOMPRESS() - Uncompressing Data
How to uncompress (restore) compressed data using the UNCOMPRESS() function? UNCOMPRESS(str) is a MySQL built-in function that uncompresses a given compressed byte string using the default LZ77 compression algorithm. For example: SELECT UNCOMPRESS(x'37000000789C738BF 44C4ECD2B492DD24BCECFD57123960 700... 2024-12-18, 2638🔥, 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, 2632🔥, 0💬

Create a New View in MySQL
How To Create a New View in MySQL? You can create a new view based on one or more existing tables by using the "CREATE VIEW viewName AS selectStatement" statement as shown in the following script: mysql&gt; CREATE TABLE comment (faqID INTEGER, message VARCHAR(256)); Query OK, 0 rows affected (0.... 2018-01-24, 2630🔥, 0💬

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, 2627🔥, 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, 2622🔥, 0💬

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General MySQL Oracle SQL Server