# WHERE in T-SQL: an overview

A WHERE clause keeps only the rows that match a condition, such as the customers in one country.

Novice · T-SQL · SQL · Updated November 3, 2026

## After this lesson you can

- Filter rows with a WHERE clause

## Key takeaways

- `WHERE` keeps only the rows where its condition is true, and it goes after `FROM` and before `ORDER BY`.
- SQL compares with a single `=` and puts text in single quotes: `WHERE Country = 'UK'`.
- SQL Server's comparisons usually ignore case, so `'uk'` matches `'UK'`.
- Numbers need no quotes: `WHERE CategoryId = 2`.

A table holds every row; usually you want only some of them. The `WHERE` clause adds a filter: only the rows that match its condition are returned.

```sql
SELECT CompanyName, City
FROM Customers
WHERE Country = 'UK';
```

| CompanyName | City |
|---|---|
| Around the Horn | London |
| B's Beverages | London |
| Consolidated Holdings | London |
| Eastern Connection | London |
| Island Trading | Cowes |
| North/South | London |
| Seven Seas Imports | London |

Of 91 customers, 7 are in the UK.

## How it works

The database looks at each row in turn and checks the condition. Rows where it's true are kept; the rest are left out. It's the `if` statement of SQL, applied to every row.

`WHERE` goes after `FROM` and before `ORDER BY`:

```sql
SELECT CompanyName, City
FROM Customers
WHERE Country = 'UK'
ORDER BY City, CompanyName;
```

## Three things that differ from C#

| SQL | C# | |
|---|---|---|
| `Country = 'UK'` | `country == "UK"` | SQL compares with a **single** `=` |
| `'UK'` | `"UK"` | SQL text goes in **single** quotes |
| `'uk'` matches `'UK'` | `"uk" != "UK"` | SQL Server's comparisons usually **ignore case** |

That last one depends on how the database was set up (its *collation*), but SQL Server's default ignores case, so `WHERE Country = 'uk'` finds the same 7 customers.

## Numbers need no quotes

Numbers are written as they are:

```sql
SELECT ProductName, UnitPrice
FROM Products
WHERE CategoryId = 2;
```

That returns the 12 products in category 2, Condiments.

## Check yourself

1 question to try on the lesson page.

## So what

Almost every query an app runs has a `WHERE`: this customer's orders, this week's sales, this product. Filtering in the database means only the rows you need ever reach your code.

## Key terms

- [WHERE](https://www.ask-codey.com/glossary/where-database)
- [Comparison Predicate](https://www.ask-codey.com/glossary/comparison-predicate)

## Cheat sheets

- [WHERE in T-SQL: an overview](https://www.ask-codey.com/cheat-sheets/where-in-t-sql-an-overview-cheat-sheet)

Source: https://www.ask-codey.com/lessons/where-in-t-sql-an-overview