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Close MySQL Connection Objects in MySQL
How To Close MySQL Connection Objects in MySQL? MySQL connection objects created with mysql_connect() calls should be closed as soon as you have finished all of your database access needs by calling mysql_close($con) function. This will reduce the consumption of connection resources on your MySQL se...
2017-11-11, 478👍, 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, 478👍, 0💬

What Are Indexes in SQL Server
What Are Indexes in SQL Server? An index is a secondary database object associated with a table to improve the retrieval performance of rows from that table. An index can be defined for a single column or multiple columns of a given table. If an index is defined on a single column of a table, the in...
2016-11-15, 478👍, 0💬

Measuring Performance of INSERT Statements in SQL Server
How To Measure Performance of INSERT Statements in SQL Server? When indexes are defined for a table, each time a new row is inserted to the table, all the indexes must be updated. This extra update work could slow down the insert statement. To find out how much slower the INSERT statements will be o...
2016-11-13, 478👍, 0💬

Rebuilding All Indexes on One Table in SQL Server
How To Rebuild All Indexes on a Single Table in SQL Server? If you have several indexes on a single table and want to rebuild all of them, you may use the "ALTER INDEX ALL ON table_name REBUILD" statement as shown in the tutorial exercise below: USE FyiCenterData; GO UPDATE fyi_links_indexed SET url...
2016-11-08, 478👍, 0💬

Pass a Parameter to a Cursor in Oracle
How To Pass a Parameter to a Cursor in Oracle? When you define a cursor, you can set a formal parameter in the cursor. The formal parameter will be replaced by an actual parameter in the OPEN cursor statement. Here is a good example of a cursor with two parameters: CREATE OR REPLACE PROCEDURE FYI_CE...
2018-07-18, 477👍, 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, 477👍, 0💬

IN - Testing Values Returned by a Subquery in SQL Server
How To Test Values Returned by a Subquery with the IN Operator in SQL Server Transact-SQL? Normally, the comparison operator IN is used against a list of specified values as in the format of: "test_value IN (value_1, value_2, ..., value_n)". But you can also replace the list of values by a subquery ...
2017-01-21, 477👍, 0💬

Determining Data Types of View Columns in SQL Server
How Column Data Types Are Determined in a View in SQL Server? When you define a view, its columns are defined through a list of expressions in the underlying SELECT statement. Their data types will be determined implicitly by the expressions. For example, if the column expression is a column name of...
2016-11-03, 477👍, 0💬

UPDATE Subquery Returning Multiple Rows in SQL Server
What Happens If the UPDATE Subquery Returns Multiple Rows in SQL Server? If a subquery is used in a UPDATE statement, it must return exactly one row for each row in the update table that matches the WHERE clause. If it returns multiple rows, SQL Server will give you an error message. To test this ou...
2016-11-02, 477👍, 0💬

"DELETED" - Old Record of an DML Event Instance in SQL Server
How To Access the Deleted Record of an Event in SQL Server? When a DML event occurs, SQL Server will prepare a temporary table called "DELETED", which contains the old record of the affected row, which is: A copy of the deleted row for a DELETE statement. A copy of the row to be updated for an UPDAT...
2016-10-24, 477👍, 0💬

"CREATE USER" - Creating a User Name in a Database in SQL Server
How To Create a User Name in a Database in SQL Server? User names are security principals at the database level. If you want to allow a login name to access a specific database, you need to create a user name in that database and link it to the login name. Creating a user name can be done by using t...
2016-10-19, 477👍, 0💬

Open and Close an Explicit Cursor in Oracle
How To Open and Close an Explicit Cursor in Oracle? An existing cursor can be opened or closed by the OPEN or CLOSE statement as shown in the following sample script: DECLARE CURSOR c_list IS SELECT * FROM countries; CURSOR t_list IS SELECT * FROM employees WHERE employee_id = 100; BEGIN OPEN c_list...
2018-07-22, 476👍, 0💬

What Is BDB in MySQL
What Is BDB (BerkeleyDB) in MySQL? BDB (BerkeleyDB) is transaction safe storage engine originally developed at U.C. Berkeley. It is now developed by Sleepycat Software, Inc. (an Oracle company now).   ⇒Database Basics and Terminologies in MySQL ⇒⇒MySQL Database Tutorials
2017-07-03, 476👍, 0💬

"CREATE LOGIN" - Creating a New Login Name in SQL Server
How To Create a New Login Name in SQL Server in SQL Server? In previous tutorials, it is assumed that you use the "sa" (System Administrator) login name to connect to your SQL Server. But that is not what a normal developer uses to connect to the server, since "sa" has the ALL permissions granted. Y...
2016-10-20, 476👍, 0💬

Connect to Oracle Server as SYSDBA in Oracle
How To Connect the Oracle Server as SYSDBA in Oracle? This is Step 4. The best way to connect to the Oracle server as an administrator is to use SQL*Plus. You need to run SQL*Plus with /nolog option and use the CONNECT with blank user name, blank password and AS SYSDBA option. Here is a sample sessi...
2019-04-03, 475👍, 0💬

Define a Variable for a Specific RECORD Type in Oracle
How To Define a Variable of a Specific RECORD Type in Oracle? Once you have your specific RECORD type defined, you can define new variables with this specific RECORD type like any other data type. In the sample script below, several variables are defined with a regular data type and a specific RECOR...
2018-09-01, 475👍, 0💬

Listing All User Accounts in MySQL
How To List All Existing User Accounts in MySQL? MySQL stores all existing user accounts in a table called "mysql.user". If you want see all user accounts, you can use the "SELECT" command as shown in the tutorial exercise below: &gt;cd \mysql\bin &gt;mysql -u root -pretneciyf mysql mysql&am...
2017-12-13, 475👍, 0💬

Show the Current Transaction Mode in MySQL
How To Find Out the Current Transaction Mode in MySQL? If you are not sure about your current transaction mode, you can use the "SELECT @@AUTOCOMMIT FROM DUAL" statement to find out as shown in the following tutorial exercise: &gt;\mysql\bin\mysql -u dev -piyf fyi mysql&gt; SELECT @@AUTOCOMM...
2016-10-17, 475👍, 0💬

Declare Local Variables in Oracle
How To Declare a Local Variable in Oracle? A local variable can be defined in the declaration part with a declaration statement, which is a variable name followed a data type identifier. Below are some examples of declaration statements: PROCEDURE proc_var_1 AS domain VARCHAR2(80); price REAL; is_fo...
2018-11-17, 474👍, 0💬

What are 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'....
2018-03-24, 474👍, 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, 474👍, 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, 473👍, 0💬

"DROP" Statements - Deleting database objects in SQL Server
How to delete database objects with "DROP" statements in SQL Server? To remove all database objects created by previous tutorials, you could just delete the database. However, in this tutorial, you will go through the steps to reverse every action you took doing the tutorial. Removing permissions an...
2016-11-27, 473👍, 0💬

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