CAST and CONVERT for type changes in SQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the CAST function do in SQL?

CAST changes a value from one data type to another in SQL. For example, it can turn a number into text or a date into a string.

intermediate

How is CONVERT different from CAST in SQL?

CONVERT also changes data types but often allows formatting options, especially for dates. CAST is more standard and simpler.

beginner

Write a SQL example using CAST to convert an integer 123 to a string.

SELECT CAST(123 AS VARCHAR(10));

intermediate

Write a SQL example using CONVERT to change a date to a string with format style 101 (mm/dd/yyyy).

SELECT CONVERT(VARCHAR(10), GETDATE(), 101);

beginner

Why might you use CAST or CONVERT in a SQL query?

To make sure data types match when comparing or combining data, or to format data for display or calculations.

Which SQL function is more standard across different database systems for type conversion?

A CONVERT

B FORMAT

C CAST

D TO_CHAR

CAST is part of the SQL standard and works in most databases, while CONVERT is often specific to certain systems like SQL Server.

What does this SQL do? SELECT CAST('2024-06-01' AS DATE);

A Converts a string to a date

B Converts a date to a string

C Changes a number to a string

D Changes a string to a number

CAST here changes the text '2024-06-01' into a date type.

Which CONVERT style code formats a date as mm/dd/yyyy in SQL Server?

A 120

B 101

C 103

D 1

Style 101 formats dates as mm/dd/yyyy in SQL Server's CONVERT function.

If you want to convert an integer to a string in SQL, which is correct?

A CAST(123 AS VARCHAR)

B CONVERT(INT, '123')

C CAST('123' AS INT)

D CONVERT(DATE, 123)

CAST(123 AS VARCHAR) converts the number 123 to a string.

Which function allows you to specify a style or format when converting types?

A SUBSTRING

B CAST

C LEN

D CONVERT

CONVERT lets you specify a style code for formatting, especially useful for dates.

Explain how CAST and CONVERT are used to change data types in SQL and when you might choose one over the other.

Think about standard use versus formatting needs.

Describe a real-life example where converting data types in SQL is necessary.

Imagine working with a report or data from different sources.