Skip to main content

Understanding T-SQL

T-SQL is the term coined by Microsoft & Sybase collaboration. It's the proprietary extension of SQL of Microsoft & Sybase. T-SQL is the main RDBMS to manage & manipulate the data in sql server. Like SQL, you don't need to write strongly type T-SQL. SQL server will parse the T-SQL into sql then execute the parsed query on top of the relational database model.

Let's try to understand the T-SQL

1. SQL is a standard of ISO & ANSI. T-SQL is a dialect of SQL.
2. Every database vendors (oracle, sybase..) implement the dialects of SQL as the main language to handle data in their database. Therefore core language element is same across all the database vendors.
3. SQL is strongly typed checked. Every SQL statement should end with semicolon (" ; ")                 T-SQL: it's not mandatory to end the every statement with " ; " semicolon.                              e.g. "Let's say we've an employee table and we want to fetch all the records"                          Using SQL syntax ( semicolon is mandatory): following query will give compilation error "SELECT * FROM Employee"                                                                                                      Using T-SQL syntax ( semicolon is optional): same query will execute successfully "SELECT * FROM Employee "
4. SQL: to get the result set from underlying table or sub-query it's mandatory to have "SELECT", "FROM" & "" T-SQL: To get the result set only "SELECT" is the mandatory key-word. Let's say you want to see the current date. Using SQL: you've to take the help of other data source "SELECT FROM Employee WHERE 1 = 0; " Or some dummy table\view provided by your database vendors "SELECT FROM DUAL ; " Using T-SQL: "SELECT GetDate() "
5. As per relational model all the attributes should have some name. But using T-SQL we can get the result-set based on the expression or column levele sub-queries without any name "SELECT Id , FirstName + ' ' + MiddleName + ' ' + LastName FROM Employees "
6. According to relational model all attributes of result-set should have unique name. T-SQL allows the query to return result-set with duplicate column-names. T-SQL example: "SELECT e.Id , d.Id FROM Employees as e JOIN Department as d ON e.DepartmentId = d.Id "

Comments

Post a Comment

Popular posts from this blog

EFCore - Collate function

Search in SQL server query is generally case insensitive (by default or based on database level collation). Suppose we have an employees table with a row having first-name column value as "My-First-Name", so if we want to do the case-sensitive search we have to explicitly use the related collate: In EF 5 (currently in Release Candidate version [RC.2.20475.6]) Collate function got introduced which helps us to use our specific collation based search.  C# with EF5 code sample: var employeeCaseSensitiveSearch = _dbContext.Employees .Where(x => EF.Functions.Collate(x.FirstName, "Latin1_General_CS_AS") == "my-first-name") .FirstOrDefault(); A related database query will be something like this: T-SQL: Case sensitive search (use specific collation e.g.: Latin1_General_CS_AS) SELECT * FROM dbo.Employees AS e WHERE e.FirstName Collate Latin1_General_CS_AS = 'my-first-name' Some of the useful CSharp function which g...
Post a Comment
Read more

Azure SQL - User management with Active Directory Group

To manage the user's roles we use Service Account on OnPrem/IaaS servers. We can use this service account on our SQL Server and accordingly manage users' permissions for the users who are part of this service account. Suppose we have an Azure SQL and we want to manage set-of-users permission shall we create each-and-every users' user profile in Azure SQL and set the permissions accordingly. Obviously, we will not .  If we've anything like Service Account (or Group) on Azure we could create the user of this GROUP on Azure SQL and set its permission/role. Here comes the Azure Active Directory Group to help us.  In case if our organization has some scheduled tasks to sync Active Directory (service account) to Azure Active Directory (AAD group), already in place, there will be some delay when we add a user to the Service account and get reflected in the AAD Group. If we have a requirement that as soon as we add a user to our group we wan...
Post a Comment
Read more

Git - Update submodule

Sometimes in the large project when we separate it in different repositories we need to take reference of one repository in another where some the sub-module concepts. Now if we move our submodule to a different repository or renaming its repo-path then we've to also update the repository where this sub-module is getting referenced. Let's see how to update the git submodule.  Step-1: First clone the repo Step-2: Open git UI to create a new local branch from master  Step-3: Open git bash -- Now run below command to (remove submodules & add them):  -- Remove submodule git submodule deinit YOUR_FIRST_REPO git rm YOUR_FIRST_REPO git commit -m "Removed submodule YOUR_FIRST_REPO" rm -rf .git/modules/YOUR_FIRST_REPO -- Add submodule git submodule add <<..YOUR_FIRST_REPO git URL>> Step-4: All good, let's push our changes to the master
Post a Comment
Read more