Getting Started with T-SQL Data Manipulation Language
You want to work with data and feel sure about it. SQL has changed to fit what people need today. T-SQL now runs on Microsoft SQL Server and Microsoft Fabric. Companies need good ways to manage data now more than ever. Many engineers and citizen developers use DML commands each day. They use them to work with information fast and correctly.
Key Takeaways
T-SQL adds more tools to standard SQL. It has things like stored procedures and error handling. These tools help you manage data more easily and quickly.
Data Manipulation Language (DML) commands are important. Commands like INSERT, UPDATE, DELETE, and MERGE help you work with your database records.
Always use the WHERE clause in UPDATE and DELETE commands. This stops you from changing all rows in a table by mistake.
Use SELECT with WHERE, ORDER BY, and DISTINCT. These help you filter, sort, and clean your data. This gives you better information.
Practice T-SQL commands on sample databases. This helps you get better and feel more sure about managing data.
T-SQL Data Manipulation Language
What is T-SQL?
You use T-SQL to work with data in Microsoft SQL Server or Microsoft Fabric. T-SQL means Transact-SQL. It adds more features to regular SQL. These features help you solve harder problems. You can use loops, if-then statements, and local variables. These tools let you write scripts that do more than simple queries. T-SQL also gives you built-in functions for working with strings, handling data, and custom error messages. These features help you work faster and make your work easier.
Here is a table that shows how T-SQL helps you compared to standard SQL:
Data Manipulation Language Overview
You use data manipulation language to change and manage information in your database. This language has commands to add, change, or remove data. These commands help keep your data correct and current. Here are the main things you can do:
INSERT: Puts new records into a table.
UPDATE: Changes records that are already in a table.
DELETE: Takes records out of a table.
MERGE: Does both INSERT and UPDATE based on certain rules.
Data manipulation language is important because it lets you work with your data in exact ways. You can add new facts, fix errors, or get rid of old records. These actions help keep your data correct and make things run better.
T-SQL and data manipulation language are very important in Microsoft SQL Server and Microsoft Fabric. You can use triggers, stored procedures, and database-level roles to manage your data and control who can see it. These tools help you work with data safely and quickly, whether you are an engineer or a citizen developer.
DML Commands
You use DML commands in SQL to work with data. These commands help you get, add, change, or remove information. You should know how each command works. This helps you manage your data well. Here is a table that shows the four main DML commands in SQL and what each one does:
You use these DML commands in SQL every day. You use SELECT to look at data. You use INSERT to add new rows. You use UPDATE to fix values in rows. You use DELETE to take out rows you do not need. Each command has its own job.
SELECT Statement
You use SELECT to get data from tables. This command lets you pick which rows and columns you want. You can use it for one table or many tables. Here is a table that shows what SELECT does and how you write it:
You use SELECT to answer questions about your data. For example, you can find all customers from a city. You can see which products sold last month. In business, you often use SELECT INTO to copy data into a temporary table. This makes it easier to work with and join data.
Tip: You can use SELECT with WHERE to filter results. You can use ORDER BY to sort them. You can use DISTINCT to remove duplicates.
INSERT Command
You use INSERT to add new rows to a table. This command helps you grow your data by putting in new records. You can insert one row or many rows at once. Here are some ways you can use INSERT in T-SQL:
When you use DML commands in SQL to insert data, you should follow best practices. Always name the columns you want to fill. Check your data before you insert it. Use transactions to keep your data safe. Batch inserts can make your work faster.
Name columns to avoid mistakes.
Use parameterized queries to keep data safe.
Check your data to make sure it fits the rules.
Use transactions to keep your data correct.
Use batch inserts for speed.
UPDATE Command
You use UPDATE to change data in your tables. This command lets you fix mistakes or update facts. You can change one column or many columns at once. You can use conditions to pick which rows to update.
Change values in columns.
Update more than one column at once.
Use WHERE to pick which rows to change.
When you use DML commands in SQL to update data, you need to be careful. If you forget WHERE, you might change every row in the table. Separate each column with a comma. Watch for case sensitivity when you compare strings.
Always use WHERE to target the right rows.
Separate columns with commas.
Watch for case sensitivity in your data.
DELETE Command
You use DELETE to remove rows from a table. This command helps you clean up old or wrong data. You can delete one row or many rows at once. Use WHERE to pick which rows to delete. If you do not use WHERE, you will delete all rows in the table.
The DELETE command in T-SQL lets you remove data you do not need. You can use it with WHERE to pick certain rows. If you leave out WHERE, you will delete everything in the table.
Note: Always check your WHERE clause before you run DELETE. This helps you avoid losing important data.
You use DML commands in SQL to keep your data correct and up to date. You use SELECT to look at data. You use INSERT to add new data. You use UPDATE to fix data. You use DELETE to remove data. These commands give you control over your database.
SELECT Statement Usage
You use the select statement in t-sql to get data from tables. This command lets you pick which rows and columns to see. You can add extra parts to your query to do more things. You can filter, sort, or take out repeats. Let’s see how select works in real life.
WHERE Clause
The where clause helps you filter your results. You only see rows that match your rules. You can use where with numbers, words, dates, or patterns. You can also use AND, OR, and NOT to mix rules.
Here is a table that shows what the where clause does:
You can use select with where to find customers from one city. You can look for products that cost more than $100. You can search for names that start with “A”.
Here are some examples:
Find products that cost more than $50:
SELECT ProductName, Price FROM Products WHERE Price > 50;
Get workers in the Sales department:
SELECT EmployeeID, Name FROM Employees WHERE Department = 'Sales';
Show orders after January 1, 2024:
SELECT OrderID, OrderDate FROM Orders WHERE OrderDate > '2024-01-01';
You can mix rules to make your select more exact. For example, you can find products with prices between $50 and $100:
SELECT ProductName, Price FROM Products WHERE Price >= 50 AND Price <= 100;
Tip: Always check your where rules. This helps you get the right data and not make mistakes.
ORDER BY Clause
Order by lets you sort your results. You can sort by one column or more. You can pick ascending (ASC) or descending (DESC) order. This helps you see your data the way you want.
Here is a table that explains order by:
You can use select with order by to list products from cheapest to most expensive:
SELECT ProductName, Price FROM Products ORDER BY Price ASC;
You can show customers from A to Z:
SELECT CustomerName FROM Customers ORDER BY CustomerName ASC;
You can sort by more than one column. For example, sort by department and then by name:
SELECT Name, Department FROM Employees ORDER BY Department, Name;
You can use DESC to show the highest prices first:
SELECT ProductName, Price FROM Products ORDER BY Price DESC;
Sorting helps you spot patterns and make reports. Use order by with select to organize your data for easy reading.
DISTINCT Keyword
Distinct helps you remove repeat rows from your results. This means you only see unique values. You can use distinct with one column or many columns.
For example, you want to see all job titles in your company. Some workers have the same job title. Use select with distinct to get each job title once:
SELECT DISTINCT JobTitle FROM HumanResources.Employee ORDER BY JobTitle;
You can use distinct to find all cities where your customers live:
SELECT DISTINCT City FROM Customers;
You can use distinct with more than one column. For example, see unique pairs of city and state:
SELECT DISTINCT City, State FROM Customers;
Distinct helps you clean up your results. Use select with distinct to get a list of unique values and avoid repeats.
Step-by-Step Examples
You can use select with different parts to answer many questions. Here is a table with examples:
You can use select with where to filter your data. You can use select with order by to sort your results. You can use select with distinct to remove repeats. You can mix these parts to make your queries even better.
Use select with where to find the data you need.
Use select with order by to organize your results.
Use select with distinct to get unique values.
Practice using select with these parts. You will get better at finding, sorting, and cleaning your data in t-sql.
Operators and Precedence
Common Operators
You use operators in T-SQL to work with data. Operators help you add, change, or remove records in your tables. You see these operators every day when you write DML commands. Here are the most common operators you use:
UPDATE helps you change values in existing records.
DELETE removes records from your table.
MERGE combines adding, changing, or deleting in one command.
You use these operators to control your data. When you use INSERT, you put new information into your database. UPDATE lets you fix mistakes or change facts. DELETE helps you clean up old or wrong data. MERGE gives you a way to do more than one action at a time.
Tip: Always check your commands before you run them. This helps you keep your data safe.
Precedence Rules
Operator precedence tells you the order in which T-SQL runs parts of your expressions. You need to know how T-SQL decides which part to run first. Operators with higher precedence run before those with lower precedence. Parentheses let you change the default order and control how T-SQL works with your data.
Operator precedence in T-SQL decides the order of operations in your expressions.
Operators with higher precedence run first.
Parentheses let you set the order you want.
For example, look at this code:
SET @MyNumber = 2 * (4 + 5);
T-SQL runs the addition inside the parentheses first. You get 2 times 9, which equals 18.
If you do not use parentheses, you might get a different result. Logical errors can happen when you do not understand operator precedence. For example, you want to check if either @x or @y equals 1 and @z equals 1. If you write:
SELECT CASE WHEN @x=1 OR @y=1 AND @z=1 THEN 'T' ELSE 'F' END
T-SQL runs AND before OR. You get 'T' even if only @x equals 1. If you want the correct logic, use parentheses:
SELECT CASE WHEN (@x=1 OR @y=1) AND @z=1 THEN 'T' ELSE 'F' END
Now, T-SQL checks if either @x or @y equals 1, and then checks if @z equals 1. You get the result you expect.
Note: Always use parentheses to set the order of your logic. This helps you avoid mistakes and get the right answer.
Quick Reference
DML Syntax Cheat Sheet
You might forget the main T-SQL commands sometimes. The table below shows each command and what it does. You can use this table as a quick guide when you write queries.
📝 Tip: Keep this table close when you use T-SQL. It helps you pick the right command for your job.
Beginner Tips
You want to make fewer mistakes and learn quickly. Here are some easy tips to help you use T-SQL DML commands:
Check your spelling for commands and table names. If you spell something wrong, your query will not work.
Watch out for uppercase and lowercase letters. Using the wrong case for a table or column name can cause problems.
Put keywords and symbols in the right order. A good query works better and is easier to read.
Use the WHERE clause to pick certain rows. This keeps your data safe and stops you from changing the wrong rows.
Try using sample databases before you use real data. This helps you get better and feel more sure.
⚡ Note: If you want to practice T-SQL, you can use online tools. SQL Problems and Solutions lets you try queries on sample tables. Essential SQL gives you step-by-step lessons for Microsoft SQL Server. Learn SQL The Hard Way teaches you with exercises. Udemy has courses for all skill levels. Khan Academy, SQLZoo, and Codecademy have fun tutorials and coding games.
You can learn T-SQL faster if you use these tools. Try out different queries and see what happens. You will get better if you practice and pay attention.
You can get good at T-SQL DML by trying each command and looking at real examples. As you learn, remember these important things:
Learn DML skills to work with data fast.
Use parameterized queries and transactions to protect your data.
Try to make your queries run better.
Keep learning new things to stay current.
Keep trying new things with T-SQL DML. You will learn how to manage data in SQL Server and other systems with confidence.
FAQ
What is the difference between T-SQL and SQL?
T-SQL means Transact-SQL. You use T-SQL with Microsoft SQL Server. T-SQL gives you more features than standard SQL. These extra features help you write better scripts. They also help you manage data more easily.
Can I undo a DELETE or UPDATE command in T-SQL?
You cannot undo these commands unless you use a transaction. If you start with BEGIN TRANSACTION, you can use ROLLBACK to undo changes. Always try your commands on test data first.
How do I avoid changing all rows by mistake?
Always use a WHERE clause in your UPDATE or DELETE statements. This helps you pick only the rows you want to change. Check your query carefully before you run it.
What is a parameterized query, and why should I use it?
A parameterized query lets you use placeholders for values. It helps keep your data safe from SQL injection attacks. It also makes your code easier to read and fix.
Where can I practice T-SQL commands safely?
You can use online tools like SQLZoo or Codecademy. You can also use sample databases in SQL Server. These places let you try queries without hurting real data.