Parts of an SQL Query

Before writing queries, learn the vocabulary. When a senior developer says "your WHERE clause has the wrong identifier" or an error says "Incorrect syntax near the keyword FROM", you need to know exactly which part of the query they mean. In this chapter every example uses our IPL players table:

• id — unique player number (primary key)
• name — player name
• team — IPL franchise code
• country — where the player is from
• runs — runs scored this season (sample numbers for learning)

Definition

An SQL query is a statement that asks the database to return data. It is built from clauses (SELECT, FROM, WHERE …), and each clause is made of smaller pieces: keywords, identifiers, functions, operators and values.

The full list of clauses a SELECT query can contain, in the order you write them:

SELECT DISTINCT TOP n  columns
FROM     table
JOIN     other_table ON ...
WHERE    row_condition
GROUP BY columns
HAVING   group_condition
ORDER BY columns

One query, eight components

-- Retrieve Indian Players
SELECT name, LOWER(team)
FROM players
WHERE country = 'India';

Result of the query:

Note: SQL Server would label the second column (No column name) because it is a calculation with no alias. You will fix that with AS in the next topic.

Rules worth remembering

• Keywords are not case-sensitive: select, SELECT and Select all work. Convention: write keywords in UPPERCASE and identifiers in lowercase so queries are easy to read.
• Text values go inside single quotes: 'India'. Numbers do not: runs > 500.
• Double quotes are for identifiers, not text in SQL Server: "country" means the column country. SQL Server also lets you wrap identifiers in square brackets: [player name] — needed when a name has spaces or is a reserved word.
• Whitespace and new lines don't matter to the database — put one clause per line for humans.
• Semicolon ; ends a statement. It is optional for most statements in SQL Server but required in some cases (e.g. before a CTE), so make it a habit.

Common mistakes

• ❌ WHERE country = "India" — in SQL Server this looks for a column named India → Invalid column name 'India'. ✅ WHERE country = 'India'.
• ❌ Naming a column with a keyword (order, select) and getting syntax errors. ✅ Choose another name or wrap it: [order].
• ❌ Forgetting that -- comments out the rest of the line, including code after it.

Interview tip

Q: What is the difference between a keyword and an identifier? A: A keyword is a reserved word defined by SQL itself (SELECT, FROM, WHERE). An identifier is a name you create for an object — a table, column, alias or view (players, runs).