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Counting Groups Returned with the GROUP BY Clause in Oracle
How To Count Groups Returned with the GROUP BY Clause in Oracle? 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 ...
2019-09-16, 542👍, 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, 542👍, 0💬

Deleting an Existing Database in MySQL
How To Drop an Existing Database in MySQL? If want to drop an existing database from the MySQL server, you can use the DROP DATABASE statement. Here is a good example of dropping an existing database: $con = mysql_connect('localhost:8888' ,'dev', 'iyf'); $sql = 'DROP DATABASE fyi'; if (mysql_query($...
2017-10-23, 542👍, 0💬

Testing Table for DML Statements in SQL Server
How To Create a Testing Table with Test Data in SQL Server? If you want to practice DML statements, like INSERT, UPDATE and DELETE statements, you should create a testing table. The tutorial exercise shows you a good example: CREATE TABLE fyi_links (id INTEGER PRIMARY KEY, url VARCHAR(80) NOT NULL, ...
2016-11-03, 542👍, 0💬

Indexes for the PRIMARY KEY Column in Oracle
What Is an Index Associated with a Constraint in Oracle? An index associated with a constraint because this constraint is required to have an index. There are two types of constraints are required to have indexes: UNIQUE and PRIMARY KEY. When you defines a UNIQUE or PRIMARY KEY constraint in a table...
2019-05-01, 541👍, 0💬

Defragmenting Table Indexes in SQL Server
How To Defragment Table Indexes in SQL Server? When a table index is fragmented to a certain percentage, you need to defragment the index to maintain its performance level. There are 3 ways to defragment: 1. "ALTER INDEX index_name ON table_name REORGANIZE" - Defragmenting the specified index perfor...
2016-11-08, 541👍, 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, 540👍, 0💬

Calculating the Difference between Two Dates in MySQL
How To Calculate the Difference between Two Dates in MySQL? If you have two dates, and you want to know how many days between them, you can use the DATEDIFF(date1, date2) function as shown below: SELECT DATEDIFF(DATE('1997-02-28'), DATE('1997-03-01')) FROM DUAL; -1   ⇒Introduction to Date and Time H...
2017-12-26, 540👍, 0💬

Database in Use When Renaming a Database in SQL Server
Why I am getting this error when renaming a database in SQL Server? If you are trying to rename a database that is in use, you will get an error message like this: "The database could not be exclusively locked to perform the operation." Before renaming a database, you must stop all client sessions u...
2016-11-20, 540👍, 0💬

What Are Cursors in SQL Server
What Are Cursors in SQL Server Transact-SQL? A cursor is a special data type that represents a result set returned by a SELECT query statement. There are several notes about cursor you need to remember: Cursor data type can not be used to define table columns. Cursor data type is used on store proce...
2016-10-17, 540👍, 0💬

Define a RECORD Variable for a Table Row in Oracle
How To Define a RECORD Variable to Store a Table Row in Oracle? If you have a table, and want to define a RECORD variable to store all the data elements of a row from that table, you can use table_name%ROWTYPE to define the RECORD variable as shown in the following sample script: CREATE TABLE studen...
2018-08-14, 539👍, 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, 539👍, 0💬

LIKE - Matching a Pattern in a Character String in SQL Server
What To Perform Pattern Match with the LIKE Operator in SQL Server Transact-SQL? Pattern match is a very important operation for search records base on character string columns. SQL Server 2005 offers the LIKE operator to perform pattern match operations in two formats: target_string LIKE pattern --...
2017-01-21, 539👍, 0💬

Creating Local Temporary Stored Procedures in SQL Server
How To Create a Local Temporary Stored Procedure in SQL Server Transact-SQL? A local temporary stored procedure is a special stored procedure that: Is created like a normal (permanent) stored procedure with the name prefixed with a number sign (#). Are only valid in the same client session where it ...
2016-12-28, 539👍, 0💬

Adding Address Records into AdventureWorksLT in SQL Server
How to add an address record into AdventureWorksLT in SQL Server? To find out if we can add data into AdventureWorksLT or not, you can try to add an address record into the "SalesLT.Address" in AdventureWorksLT: USE AdventureWorksLT GO INSERT SalesLT.Address (AddressLine1, City, StateProvince, Count...
2016-12-02, 539👍, 0💬

Relation between Database and Tablespaces in Oracle
How a Database Is Related to Tablespaces in Oracle? A database's data is collectively stored in the datafiles that constitute each tablespace of the database. For example, the simplest Oracle database would have one tablespace and one datafile. Another database can have three tablespaces, each consi...
2019-01-20, 538👍, 0💬

Show Free Space in a Tablespace in Oracle
How To See Free Space of Each Tablespace in Oracle? One of the important DBA tasks is to watch the storage usage of all the tablespaces to make sure there are enough free space in each tablespace for database applications to function properly. Free space information can be monitored through the USER...
2019-01-01, 538👍, 0💬

Creating an Index for Multiple Columns in SQL Server
How To Create an Index for Multiple Columns in SQL Server? An index for multiple columns works similarly to a sorting process on multiple columns. If an index is defined for two columns, the index key is composed by values from those two columns. A multi-column index will be used to speed up the sea...
2016-11-13, 538👍, 0💬

"INSERT INTO" - Inserting a New Row into a Table in SQL Server
How To Insert a New Row into a Table with "INSERT INTO" Statements in SQL Server? To insert a new row into a table, you can use the INSERT INTO statement with values specified for all columns as in the following syntax: INSERT INTO table_name VALUES (list_of_values_of_all columns) Note that the list...
2016-11-03, 538👍, 0💬

Rolling Back the DDL Statement in a Trigger in SQL Server
Can You Roll Back the DDL Statement in a Trigger in SQL Server? Can you roll back the DDL statement in a trigger? The answer is yes. Since the DDL statement that fires the trigger and the statements defined inside the trigger are all executed as a single statement batch, you can add a ROLLBACK state...
2016-10-22, 538👍, 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, 537👍, 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, 537👍, 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, 537👍, 0💬

Creating a Large Table with Random Data for Indexes in SQL Server
How To Create a Large Table with Random Data for Index Testing in SQL Server? If you want to see how index can be used to improve data search performance, you have to build some large tables, which requires large amount of random data. This tutorial exercise helps you to build a large table with pur...
2016-11-13, 537👍, 0💬

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