Data Types

When you create a table you must tell SQL what kind of value each column will hold. Runs are whole numbers, names are text, a debut is a calendar date, a strike rate has decimals. Choosing the right data type keeps your data clean, makes queries faster and stops mistakes like someone typing 'seven hundred' into a runs column.

Definition

A data type is a rule attached to a column that defines which kind of values the column can store (numbers, text, dates…), how much space each value may take, and which operations make sense on it.

• Which kind of values — an INT column rejects 'Virat'; a DATE column rejects 'hello'.
• How much space — VARCHAR(50) allows at most 50 characters; DECIMAL(5,2) allows at most 5 digits.
• Which operations — you can add two INTs, find the year of a DATE, or take LEFT() of a VARCHAR.

Every column must have a data type — you cannot create a column without one in SQL Server.

The 4 types that cover most IPL data

Understanding the numbers in brackets

VARCHAR(n) — n is the maximum number of characters. VARCHAR(10) fits 'RCB' (3 characters) and only uses space for those 3 characters — that is the "variable" in VARCHAR. In SQL Server, trying to store more than n characters raises the error "String or binary data would be truncated."

DECIMAL(p, s) — two numbers:

So DECIMAL(5,2) can store values from -999.99 to 999.99. 139.50 fits (3 digits before, 2 after). 1395.00 does not fit (4 digits before the point).

Other common SQL Server data types

Tip: CHAR(10) always uses 10 characters of space and pads short values with spaces. VARCHAR(10) only uses what it needs. For names, always prefer VARCHAR.

Example — a table using all four types

CREATE TABLE player_stats (
    id          INT,
    name        VARCHAR(50),
    debut       DATE,
    strike_rate DECIMAL(5,2)
);

INSERT INTO player_stats (id, name, debut, strike_rate)
VALUES (1, 'Virat Kohli', '2008-04-18', 139.50);

SELECT * FROM player_stats;

Result in SQL Server:

How it works: '2008-04-18' is written as text in the 'YYYY-MM-DD' format and SQL Server converts it into a real DATE. Because strike_rate is DECIMAL(5,2), SQL Server always shows exactly 2 decimal places.

Note (playground): The browser playground runs on SQLite, which is relaxed about types. It shows 139.5 instead of 139.50, and it does not reject a 60-character name in a VARCHAR(50) column. Real SQL Server is strict — trust the rules on this page.

Choosing the right type — rules of thumb

1. Numbers you calculate with → numeric types (INT, DECIMAL). Never store runs as text — '90' > '100' is TRUE in text comparison!
2. Numbers you never calculate with (phone numbers, PIN codes) → text (VARCHAR) — they can have leading zeros and +91.
3. Dates → DATE/DATETIME2, never VARCHAR — otherwise you lose YEAR(), DATEDIFF() and correct sorting.
4. Money / exact decimals → DECIMAL, not FLOAT.
5. Size it sensibly — VARCHAR(50) for names, not VARCHAR(MAX) for everything.

Common mistakes

• ❌ debut VARCHAR(20) ✅ debut DATE — text dates sort wrongly and can't use date functions.
• ❌ strike_rate INT ✅ strike_rate DECIMAL(5,2) — INT would cut 139.50 down to 139.
• ❌ DECIMAL(3,2) for a strike rate ✅ DECIMAL(5,2) — DECIMAL(3,2) only allows values up to 9.99.
• ❌ VARCHAR with no length in SQL Server — inside CREATE TABLE it silently means VARCHAR(1)! ✅ Always give a length.

SQL Server vs MySQL / PostgreSQL

Interview tip

Q: What is the difference between CHAR and VARCHAR? A: CHAR(n) is fixed-length — it always uses n characters of storage and pads shorter values with spaces. VARCHAR(n) is variable-length — it stores only the characters you actually give (up to n) plus a small length overhead. Use CHAR for values that are always the same length (like 3-letter team codes) and VARCHAR for everything else.