Final answer:
The 'FROM' clause in T-SQL specifies the tables or views from which to retrieve data within a SELECT statement. It's essential for the SQL engine to understand the data source, especially when performing table joins and querying data from multiple sources.
Step-by-step explanation:
The 'FROM' clause in T-SQL, which stands for Transact-SQL, is used to indicate the tables or views from which to retrieve data. When you're writing a SELECT statement to query a database, the FROM clause is where you specify the source of the data you want to select. Without it, the SQL engine wouldn't know where to look for the data you're asking for.
For example, if you want to get the names and addresses from a table called Customers, your query would look like this:
SELECT Name, Address FROM Customers;
This clause becomes even more important when you are joining two or more tables. In such cases, the FROM clause is where you specify the relationships between the tables and how the data should be combined.
Here is an example of a query that joins two tables, customers and orders:
SELECT Customers.Name, Orders.OrderDate FROM Customers JOIN Orders ON Customers.CustomerID = Orders.CustomerID;