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Using CASE Expression in MySQL
How To Use CASE Expression in MySQL? There are 2 ways to use the CASE expression. The first way is to return one of the predefined values based on the comparison of a given value to a list of target values. The second way is to return one of the predefined values based on a list of conditions. Here ...
2018-03-24, 418👍, 0💬

Returning Top 5 Rows in MySQL
How To Return Top 5 Rows in MySQL? If you want the query to return only the first 5 rows, you can use the LIMIT clause, which takes one parameter as the maximum number of rows to return. The following statement returns the first 5 rows from the fyi_links: mysql&gt; SELECT id, url, counts, tag FR...
2017-12-21, 418👍, 0💬

sys.indexes - Viewing Existing Indexes on an Given Table in SQL Server
How To View Existing Indexes on an Given Table using sys.indexes in SQL Server? Another way to view existing indexes defined for a given table is to use the system view called "sys.indexes". The tutorial exercise shows you how many indexes were defined from the previous tutorial on table "fyi_links"...
2016-11-15, 418👍, 0💬

Converting Character Strings to Numeric Values in MySQL
How To Convert Character Strings to Numeric Values in MySQL? You can convert character strings to numeric values by using the CAST(string AS DECIMAL) or CAST(string AS SIGNED INTEGER) function as shown in the following examples: SELECT CAST('4123.45700' AS DECIMAL) FROM DUAL; 4123.46 -- Very poor co...
2018-03-28, 417👍, 0💬

Use Existing Column Values in the SET Clause in MySQL
How To Use Existing Column Values in the SET Clause in MySQL? If a row matches the WHERE clause in a UPDATE statement, existing values in this row can be used in expressions to provide new values in the SET clause. Existing values are represented by column names in the expressions. The tutorial exer...
2018-01-13, 417👍, 0💬

What Are Group Functions in MySQL
What Are Group Functions in MySQL? Group functions are functions applied to a group of rows. Examples of group functions are: COUNT(*) - Returns the number of rows in the group. MIN(exp) - Returns the minimum value of the expression evaluated on each row of the group. MAX(exp) - Returns the maximum ...
2018-01-06, 417👍, 0💬

NULL Values Involved in String Operations in SQL Server
What Happens If NULL Values Are Involved in String Operations in SQL Server Transact-SQL? If NULL values are involved in string operations, the result will be string NULL values. The following tutorial script shows you some good examples: SELECT 'FyiCenter'+NULL; GO ---------- NULL SELECT LEN(NULL);...
2017-02-05, 417👍, 0💬

Verifying a Login Name with SQLCMD Tool in SQL Server
How To Verify a Login name with SQLCMD Tool in SQL Server? The quickest way to verify a login name on a SQL Server is probably to use the SQLCMD tool, which takes the server name, login name and password in a single command line. Here is how to try it yourself: Start a command window and enter the f...
2016-10-20, 417👍, 0💬

"DROP LOGIN" - Deleting a Login Name in SQL Server
How To Delete a Login Name in SQL Server? If you don't want to keep a login name any more, you should delete it by using the "DROP LOGIN" statement as shown in this tutorial example: -- Login with "sa" DROP LOGIN Dba_Login; GO Command(s) completed successfully. -- View login names SELECT name, sid, ...
2016-10-19, 417👍, 0💬

Loop through a Cursor Variable in Oracle
How To Loop through a Cursor Variable in Oracle? Once a cursor variable is opened with a query statement, it will have the same attributes as a normal cursor and it can be used in the same way a normal cursor too. The following sample script shows you how to loop through a cursor variable: CREATE OR...
2018-07-18, 416👍, 0💬

Start an Oracle Instance in Oracle
How To Start an Oracle Instance in Oracle? This is Step 6. Now you are ready to start the new Oracle Instance without any database. This instance will be used to create a database. Starting an instance without database can be done by using STARTUP NOMOUNT statement as shown below: &gt;.\bin\sqlp...
2018-05-08, 416👍, 0💬

Managing Databases and Physical Files in SQL Server
Where to find answers to frequently asked questions on Managing Databases and Physical Files in SQL Server? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Managing Databases and Physical Files in SQL Server. Clear answers are provided with tutori...
2016-11-24, 416👍, 0💬

Using Multiple Columns in the GROUP BY Clause in SQL Server
Can Multiple Columns Be Used in GROUP BY in SQL Server? If you want to break your output into smaller groups, you can specify multiple column names or expressions in the GROUP BY clause. Output in each group must satisfy a specific combination of the expressions listed in the GROUP BY clause. The mo...
2016-10-25, 416👍, 0💬

"INSTEAD OF" - Overriding DML Statements with Triggers in SQL Server
How To Override DML Statements with Triggers in SQL Server? Sometime, you may want to implement some business logics in a DML trigger to cancel the DML statement. For example, you may want to check the new email address format provided by the UPDATE statement. If the email address is invalid, you to...
2016-10-22, 416👍, 0💬

Define DSN with ODBC Manager in Oracle
How To Define a Data Source Name (DSN) in ODBC Manager in Oracle? DSN (Data Source Name) is an ODBC connection identifier for Windows applications. Here is how you can define a DSN on your Windows system: Go to Control Panel. Go to Administrative Tools. Run Data Sources (ODBC). Go to System DSN tab....
2016-10-15, 416👍, 0💬

Formal Parameters and Actual Parameters in Oracle
What Is the Difference between Formal Parameters and Actual Parameters in Oracle? Formal parameter and actual parameter are two different terms related parameters used in the procedures and functions: A formal parameter is a term used to refer to a parameter defined in the procedure or function decl...
2018-03-18, 415👍, 0💬

Use "mysql" to Run SQL Statements in MySQL
How To Use "mysql" to Run SQL Statements in MySQL? If you want to run SQL statement to your server with "mysql", you need to start "mysql" and enter your SQL statement at the "mysql" prompt. Here is a good tutorial exercise that shows you how to run two SQL statements with "mysql": &gt;cd \mysql...
2018-02-28, 415👍, 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, 415👍, 0💬

Decrementing a Date by 1 in MySQL
How To Decrement Dates by 1 in MySQL? If you have a date, and you want to decrement it by 1 day, you can use the DATE_SUB(date, INTERVAL 1 DAY) function. You can also use the date interval subtraction operation as "date - INTERVAL 1 DAY". The tutorial exercise below gives you some good examples: SEL...
2017-12-26, 415👍, 0💬

Restore Tables by Copying MyISAM Files in MySQL
How To Restore Tables by Copying MyISAM Table Files in MySQL? If you have old copies of MyISAM table files, you can restore them easily by copying them back to the data directory to replace the current table files. However you may need to shut down MySQL server to do this, because the current table ...
2017-09-01, 415👍, 0💬

Experiment with Dead Locks in MySQL
How To Experiment Dead Locks in MySQL? If you want to have some experience with dead locks, you can create two windows running two mysql transactions in two sessions at the REPEATABLE READ transaction isolation level. Then run some UPDATE statements as shown in the tutorial exercise below: (session ...
2017-07-21, 415👍, 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, 414👍, 0💬

Deleting an Existing Row from a Table in MySQL
How To Delete an Existing Row from a Table in MySQL? If you want to delete an existing row from a table, you can use the DELETE statement with a WHERE clause to identify that row. Here is good sample of DELETE statements: mysql&gt; INSERT INTO fyi_links (url, id) VALUES ('www.myspace.com', 301);...
2018-01-08, 414👍, 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, 414👍, 0💬

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