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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, 690👍, 0💬

Use Values from Other Tables in UPDATE in Oracle
How To Use Values from Other Tables in UPDATE Statements in Oracle? If you want to update values in one with values from another table, you can use a subquery in the SET clause. The subquery should return only one row for each row in the update table that matches the WHERE clause. The tutorial exerc...
2020-01-21, 689👍, 0💬

Groups of Data Types in MySQL
How Many Groups of Data Types in MySQL? MySQL support 3 groups of data types as listed below: String Data Types - CHAR, NCHAR, VARCHAR, NVARCHAR, BINARY, VARBINARY, TINYBLOB, TINYTEXT, BLOB, TEXT, MEDIUMBLOB, MEDIUMTEXT, LONGBLOB, LONGTEXT, ENUM, SET Numeric Data Types - BIT, TINYINT, BOOLEAN, SMALL...
2018-04-21, 689👍, 0💬

Connecting to MySQL Server on a Specific Port in MySQL
How To Connect to MySQL Server on a Different Port in MySQL? If your MySQL server is listening on port number different than 3306, you need to specify "--port=portNumber" option to any client program that needs to connect to the server. The tutorial exercise shows you how to connect "mysql" to start...
2017-11-25, 689👍, 0💬

Entering Date and Time Values in SQL Server
How To Enter Date and Time values in SQL Server Transact-SQL? Transact-SQL does not support date and time literals. If you want to enter date and time values, you have to use character string literals and rely implicit casting rules to convert them into date and time values. When casting character s...
2017-04-15, 689👍, 0💬

Update Values on Multiple Rows in Oracle
How To Update Values on Multiple Rows in Oracle? If the WHERE clause in an UPDATE matches multiple rows, the SET clause will be applied to all matched rows. This rule allows you to update values on multiple rows in a single UPDATE statement. Here is a good example: UPDATE fyi_links SET counts = 9, n...
2020-01-21, 688👍, 0💬

Sort the Query Output in Oracle
How To Sort the Query Output in Oracle? If you want the returning rows to be sorted, you can specify a sorting expression in the ORDER BY clause. The following select statement returns rows sorted by the values in the "manager_id" column: SQL&gt; SELECT * FROM departments ORDER BY manager_id; DE...
2019-12-19, 688👍, 0💬

Converting Character Strings to Dates in MySQL
How To Convert Character Strings to Dates in MySQL? If you have a character string that represents a date, and you want to convert it into a date value, you can use the STR_TO_DATE(string, format) function. STR_TO_DATE() shares the same formatting codes with DATE_FORMAT() function. The tutorial exer...
2017-12-26, 688👍, 0💬

Using Subqueries in the FROM Clause in MySQL
How To Use Subqueries in the FROM clause in MySQL? If you have a query returning many rows of data, and you want to perform another query on those rows, you can put the first query as a subquery in the FROM clause of the second query. A subquery used in this way become a temporary table, and you mus...
2017-12-21, 687👍, 0💬

Using Multiple Columns in GROUP BY in MySQL
Can Multiple Columns Be Used in GROUP BY in MySQL? If you want to break your output into smaller groups, if you 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 more col...
2017-10-16, 687👍, 0💬

Difference Between Clustered and Non-Clustered Indexes in SQL Server
What Is the Difference Between Clustered and Non-Clustered Indexes in SQL Server? SQL Server 2005 supports two types of indexes: clustered index and non-clustered index. Here are the main differences between them: One table can only have only one clustered index. One table can only have many non-clu...
2016-11-13, 687👍, 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, 686👍, 0💬

Number of Rows Selected or Affected in MySQL
How To Get the Number of Rows Selected or Affected by a SQL Statement in MySQL? There are two functions you can use the get the number of rows selected or affected by a SQL statement: mysql_num_rows($res) - Returns the number of rows selected in a result set object returned from SELECT statement. my...
2017-10-08, 686👍, 0💬

What Is Oracle Server Autotrace in Oracle
What Is Oracle Server Autotrace in Oracle? Autotrace is Oracle server feature that generates two statement execution reports very useful for performance tuning: Statement execution path - Shows you the execution loop logic of a DML statement. Statement execution statistics - Shows you various execut...
2020-06-08, 685👍, 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, 685👍, 0💬

Transaction Committed when START TRANSACTION Executed in MySQL
What Happens to the Current Transaction If a START TRANSACTION Is Executed in MySQL? If you are in a middle of a current transaction, and a START TRANSACTION command is executed, the current transaction will be committed and ended. All the database changes made in the current transaction will become...
2016-10-17, 685👍, 0💬

Commit the Current Transaction in Oracle
How To Commit the Current Transaction in Oracle? If you have used some DML statements updated some data objects, and you want to have the updates to be permanently recorded in the database, you can use the COMMIT statement. It will make all the database changes made in the current transaction become...
2019-09-04, 684👍, 0💬

Define Variables before Procedures and Functions in Oracle
What Is the Order of Defining Local Variables and Sub Procedures/Functions in Oracle? In the declaration part, you must define all local variables before defining any sub procedures or sub functions. See the following sample script: SQL&gt; CREATE OR REPLACE PROCEDURE WELCOME AS 2 SITE CHAR(80) ...
2018-03-18, 684👍, 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, 684👍, 0💬

Commit the Current Transaction in MySQL
How To Commit the Current Transaction in MySQL? If you have used some DML statements updated some data objects, and you want to have the updates to be permanently recorded in the database, you can use the COMMIT command. It will make all the database changes made in the current transaction become pe...
2016-10-17, 684👍, 0💬

Create a New View in Oracle
How To Create a New View in Oracle? You can create a new view based on one or more existing tables by using the CREATE VIEW statement as shown in the following script: CREATE VIEW employee_department AS SELECT e.employee_id, e.first_name, e.last_name, e.email, e.manager_id, d.department_name FROM em...
2020-02-07, 683👍, 0💬

Create Additional Tablespaces in Oracle
How To Create Additional Tablespaces for an New Database in Oracle? This is Step 8. Creating additional tablespaces can be done by using the CREATE TABLESPACE statement as shown in the following sample script: SQL&gt; CREATE TABLESPACE users 2 DATAFILE '/oraclexe/oradata/FYI/users01 .dbf'SIZE 10...
2019-03-27, 683👍, 0💬

Generating CREATE PROCEDURE Scripts on Existing Stored Procedures in SQL Server
How To Generate CREATE PROCEDURE Script on an Existing Stored Procedure in SQL Server Transact-SQL? If you want to know how an existing stored procedure was created, you can use SQL Server Management Studio to automatically generate a "CREATE PROCEDURE" script The following tutorial shows you how to...
2017-01-05, 683👍, 0💬

UNIQUE Constraint Creating Default Index in SQL Server
Does the UNIQUE Constraint Create an Index in SQL Server? If you add the UNIQUE constraint on a column, SQL Server will automatically add a non-clustered index for that column. The tutorial exercise below shows you the index created as part of the UNIQUE column, "id", of "fyi_links": USE FyiCenterDa...
2016-11-13, 683👍, 0💬

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