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What Is a Data Lock in MySQL
What Is a Data Lock in MySQL? MySQL uses two types of data locks at two levels to provide you the transaction isolation level you need: Share Lock at Row Level (S) - A data row is locked by a transaction for reading. Exclusive Lock at Row Level (X) - A data row is locked by a transaction for updatin...
2017-04-28, 355👍, 0💬

DATEDIFF() - Calculating DATETIME Value Differences in SQL Server
How To Calculate DATETIME Value Differences Using the DATEDIFF() Function in SQL Server Transact-SQL? If you want to calculate the difference between two date and time values, you can use the DATEDIFF() function in the following format: DATEDIFF(datepart, startdate, enddate) returns INT: "startdate"...
2017-02-20, 355👍, 0💬

"IF ... ELSE IF ..." Statement Structures in SQL Server
How To Use "IF ... ELSE IF ..." Statement Structures in SQL Server Transact-SQL? "IF ... ELSE IF ..." statement structure is used to select one of the specified statements to be executed based on specified Boolean conditions. Here is the syntax of "IF ... ELSE IF ..." statement structure: IF conditi...
2017-01-11, 355👍, 0💬

Approximate Numeric Literals in SQL Server Transact-SQL
What are approximate numeric literals supported in SQL Server Transact-SQL? Approximate numeric literals in Transact-SQL are numbers written in scientific notation formats. Approximate numeric literals are used to provide values to approximate numeric variables or table columns like LOAT(24), DOUBLE...
2017-05-05, 354👍, 0💬

Looping through Query Output Rows in MySQL
How To Query Tables and Loop through the Returning Rows in MySQL? The best way to query tables and loop through the returning rows is to run the SELECT statement with the mysql_query() function, catch the returning object as a result set, and loop through the result with the mysql_fetch_assoc() func...
2017-06-28, 352👍, 0💬

What Is a Dead Lock in MySQL
What Is a Dead Lock in MySQL? A dead lock is phenomenon happens between two transactions with each of them holding a lock that blocks the other transaction as shown in the following diagram: (transaction 1) (transaction 2) update row X to create lock 1 update row Y to create lock 2 update row X (blo...
2017-04-28, 352👍, 0💬

Getting Year, Month and Day Out of DATETIME Values in SQL Server
How To Get Year, Month and Day Out of DATETIME Values in SQL Server Transact-SQL? You can use DATEPART() to get any part of the DATETIME value. But to get year, month and day, you can use 3 specific functions: YEAR(), MONTH() and DAY(). These functions are equivalent to DATEPART() as: YEAR(date) = D...
2017-02-14, 352👍, 0💬

Unicode String Literals in SQL Server Transact-SQL
What are Unicode string literals supported in SQL Server Transact-SQL? Unicode string literals in Transact-SQL are sequences of characters enclosed in single quotes and prefixed with (N) as N'...'. String literals are used to provide values to string variables or table columns like NCHAR(40), NVARCH...
2017-05-05, 351👍, 0💬

Breaking Query Output into Pages in MySQL
How To Break Query Output into Pages in MySQL? If you have a query that returns hundreds of rows, and you don't want to present all of them to your users on a single page. You can break output into multiple pages, and only present 10 rows per page like what Google Website is doing. To do this, you n...
2017-06-28, 349👍, 0💬

sys.sql_modules - Getting Stored Procedure Definitions Back in SQL Server
How To Get the Definition of a Stored Procedure Back in SQL Server Transact-SQL? If you want get the definition of an existing stored procedure back from the SQL Server, you can use the system view called sys.sql_modules, which stores definitions of views and stored procedures. The sys.sql_modules h...
2017-01-05, 348👍, 0💬

Comments in SQL Server Transact-SQL Statements
How to enter comments in SQL Server Transact-SQL statements? There are 2 ways to enter comments within Transact-SQL statements: Starting comments with two dashes "--": Everything between "--" and the end of the line is treated as a comment. Entering comments between "/*" and "*/": Everything between...
2017-05-29, 347👍, 0💬

Query Multiple Tables Jointly in MySQL
How To Query Multiple Tables Jointly in MySQL? If you want to query information stored in multiple tables, you can use the SELECT statement with a WHERE condition to make an inner join. Assuming that you have 3 tables in a forum system: "users" for user profile, "forums" for forums information, and ...
2017-06-23, 346👍, 0💬

Exact Numeric Literals in SQL Server Transact-SQL
What are exact numeric literals supported in SQL Server Transact-SQL? Exact numeric literals in Transact-SQL are numbers written in standard signed decimal formats. Exact numeric literals are used to provide values to exact numeric variables or table columns like INTEGER, DECIMAL(8,2), MONEY, etc. E...
2017-05-05, 346👍, 0💬

bin2hex - Converting Binary Strings into Hexadecimal Character Strings in SQL Server
How To Convert Binary Strings into Hexadecimal Character Strings in SQL Server? When a query returns a binary string value to the client tool, it will be displayed by the client tool as hexadecimal digits in a character string format. But they are hexadecimal digits on the display window, not in the...
2017-02-25, 345👍, 0💬

Load Data through External Tables in Oracle
How To Load Data through External Tables in Oracle? If you have data stored in external files, you can load it to database through an external table by the steps below: Create an external table with columns matching data fields in the external file. Create a regular table with the same columns. Run ...
2016-11-27, 343👍, 0💬

Converting Numeric Data Types by Assignment Operations in SQL Server
How To Convert Numeric Expression Data Types by Assignment Operations in SQL Server Transact-SQL? An assignment operation is used to assign an expression to a variable, a column, or a parameter. If the data type of the expression does not match the data type of the receiving variable, column, or par...
2017-03-27, 342👍, 0💬

sys.database_principals - Listing All User Names in SQL Server
How To List All User Names in a Database in SQL Server? If you want to see a list of all user names defined in a database, you can use the system view, sys.database_principals as shown in this tutorial exercise: -- Login with sa -- Select a database USE FyiCenterData; GO -- List all user names SELEC...
2017-08-25, 341👍, 0💬

Experiment with Data Locks in MySQL
How To Experiment Data Locks in MySQL? If you want to have some experience with data locks, you can create two windows running two mysql transactions in two sessions. In session 1, you can run a UPDATE statement with REPEATABLE READ transaction isolation level to create an exclusive lock. Before com...
2017-04-28, 341👍, 0💬

BEGIN ... END Statement Blocks in SQL Server Transact-SQL
How to put statements into a statement block in SQL Server Transact-SQL? You can put statements into a statement block with BEGIN and END key words in Transact-SQL using these syntaxes BEGIN statement_1 statement_2 ... END Statement blocks are mainly used with logical conditions and control-of-flow ...
2017-01-11, 341👍, 0💬

Updating Existing Rows in MySQL
How To Update Existing Rows in a Table in MySQL? Updating existing rows in a table requires to run the UPDATE statement with a WHERE clause to identify the row. The following sample script updates one row with two new values: &lt;?php include "mysql_connection.php"; $sql = "UPDATE fyi_links SET ...
2017-06-28, 340👍, 0💬

Creating a View with Data from Another View in SQL Server
Can You Create a View using Data from Another View in SQL Server? Can You Create a View with Data from Another View? The answer is yes. A view can be used as a table to build other views. The tutorial exercise below shows you how to create a view using data from another view: USE AdventureWorksLT; G...
2016-11-05, 340👍, 0💬

Tables Using BDB Storage Engine in MySQL
How To Create a New Table Using the BDB Storage Engine in MySQL? BDB (BerkeleyDB) storage engine was originally developed at U.C. Berkeley. It is now maintained by Sleepycat Software, Inc., which is an Oracle company now. BDB is transaction safe, and has been used in products from many companies, li...
2017-08-13, 337👍, 0💬

SET Statements in SQL Server Transact-SQL
How to assign value to a variable in SQL Server Transact-SQL? How to use the SET statements? In Transact-SQL, you can use SET statements to assign values to variables using the assignment operator =, in the syntax of: SET @variable = &lt;value&gt; When an SET statement is executed, the syste...
2017-04-04, 337👍, 0💬

Get System Date and Time in SQL Server Transact-SQL
How to get system date and time in SQL Server Transact-SQL? I want a list of functions for getting current system date and time. Here is a comparison of all functions that you can use to get the current date and time from the data base server system: Function Return type Precision ------------------...
2017-02-25, 337👍, 0💬

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