LENGTH and CHAR_LENGTH in MySQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the LENGTH() function return in MySQL?

LENGTH() returns the number of bytes used by a string, counting each byte including multi-byte characters.

beginner

What does the CHAR_LENGTH() function return in MySQL?

CHAR_LENGTH() returns the number of characters in a string, counting multi-byte characters as one character each.

intermediate

How do LENGTH() and CHAR_LENGTH() differ when used on a string with multi-byte characters?

LENGTH() counts bytes, so multi-byte characters count as multiple bytes. CHAR_LENGTH() counts characters, so each multi-byte character counts as one.

intermediate

Example: What is the result of LENGTH('café') and CHAR_LENGTH('café') if 'é' is a 2-byte character?

LENGTH('café') returns 5 (4 letters + 1 extra byte for 'é'), CHAR_LENGTH('café') returns 4 (four characters).

intermediate

Why is it important to use CHAR_LENGTH() instead of LENGTH() when counting characters in multi-byte strings?

Because LENGTH() counts bytes, it can overcount characters in multi-byte strings. CHAR_LENGTH() gives the true character count, which is often what you want.

What does LENGTH('hello') return in MySQL?

A 4

B 6

C 5

D 0

Each character in 'hello' is one byte, so LENGTH returns 5.

If 'é' is stored as 2 bytes, what does CHAR_LENGTH('café') return?

A 5

B 2

C 6

D 4

CHAR_LENGTH counts characters, so 'café' has 4 characters.

Which function counts bytes in a string in MySQL?

A CHAR_LENGTH()

B LENGTH()

C COUNT()

D SUBSTRING()

LENGTH() counts bytes, CHAR_LENGTH() counts characters.

What is the difference between LENGTH() and CHAR_LENGTH()?

A LENGTH counts bytes, CHAR_LENGTH counts characters

B LENGTH counts characters, CHAR_LENGTH counts bytes

C Both count characters

D Both count bytes

LENGTH counts bytes, CHAR_LENGTH counts characters.

Which function should you use to get the number of characters in a UTF-8 string?

A CHAR_LENGTH()

B LENGTH()

C ASCII()

D BIT_LENGTH()

CHAR_LENGTH() returns the number of characters, correctly handling multi-byte UTF-8 characters.

Explain the difference between LENGTH() and CHAR_LENGTH() in MySQL.

Think about how multi-byte characters are stored and counted.

When should you use CHAR_LENGTH() instead of LENGTH()?

Consider strings with accented or special characters.