T-SQL Syntax Basics

T-SQL statements are the individual instructions you send to the engine — a CREATE TABLE, an INSERT, a SELECT. Each statement is conventionally terminated with a semicolon, and while SQL Server has historically tolerated omitting it in many cases, newer statements (like THROW) require it and Microsoft recommends always including one. A batch is a group of one or more statements sent to the server together for parsing and execution as a unit; GO is the signal client tools like SSMS and sqlcmd use to mark the end of a batch, though GO itself is a client-side convention, not a T-SQL keyword.

Object names (tables, columns) are called identifiers; if a name contains spaces, starts with a digit, or collides with a reserved keyword, you must quote it using square brackets, like [Order Date] or [Group]. Comments come in two styles: -- starts a single-line comment, while /* ... */ wraps a multi-line block. String literals use single quotes, like 'hello', and prefixing a string with N, as in N'café', tells SQL Server to treat it as Unicode (nvarchar) text rather than the default non-Unicode (varchar) interpretation — important when your data includes characters outside the basic Latin alphabet.

Local variables are declared with DECLARE, prefixed with @, and given a data type: DECLARE @Count INT. You assign values with SET (one variable at a time) or SELECT (which can assign several at once, or pull a value from a query). Control-of-flow is limited but functional: IF ... ELSE branches based on a condition, and WHILE repeats a block while a condition remains true. Because IF and WHILE each control only the single statement that follows, BEGIN ... END is used to group multiple statements into one logical block when needed.

GO is not a T-SQL statement — it's a batch separator understood by client tools like SSMS and sqlcmd, telling the tool to send everything accumulated so far to the server as one batch and start collecting a fresh one. This matters because certain statements (like CREATE PROCEDURE) must be the first statement in a batch, and because local variables declared in one batch cease to exist in the next — each GO effectively resets local variable scope, even though it doesn't affect server-side objects like tables you've already created.