This Create Constraints Quiz adds a CHECK constraint WITH NOCHECK to a table that already holds a bad row. The bad row stays, and the constraint is marked not trusted. A tested script proves it, shows what trust changes for the optimizer and lists four ways to create a constraint.
CHAR, VARCHAR, NVARCHAR and VARCHAR(MAX) Quiz: How Many Bytes?
This CHAR, VARCHAR, NVARCHAR and VARCHAR(MAX) Quiz stores the text abc in three columns and asks how many bytes each one uses. The answer is 10, 3 and 6. A tested script proves it and shows the trailing space trap, the question mark problem and the 8,000 byte limit.
WHERE Clause Quiz: Why Can’t It See My Column Alias?
This WHERE Clause Quiz asks what happens when a query filters on a column alias. The answer is error 207, because WHERE runs before SELECT. A tested script shows three working fixes and a trap where an alias hides a real column.
Checking Data Fits Before Narrowing a Column Data Type
Check existing values before narrowing a column, account for dependencies and data loss, and plan the locking cost of the change.
Finding Every Object That Uses a Column
Find an object that uses a column with dependency metadata and module text search, then check dynamic SQL and application code.
Computed Column Data Types: Why the Result Type Surprises You
Your table accepts every insert, then the report dies with an overflow error. Here is why the type is inherited and the cast that fixes it.
Finding Column Definitions Without the Documentation
Find column definitions in SQL Server with sys.columns, sys.types, and sys.all_columns, including length, nullability, and system objects.