LENGTH and CHAR_LENGTH in SQL - Step-by-Step Execution

Concept Flow - LENGTH and CHAR_LENGTH

Input String

↓

Output: Numeric Value

LENGTH counts bytes in a string, CHAR_LENGTH counts characters. They differ when string has multi-byte characters.

Execution Sample

SQL

SELECT LENGTH('café'), CHAR_LENGTH('café');

This query returns the byte length and character length of the string 'café'.

Execution Table

Step	Function	Input String	Output Value	Explanation
1	LENGTH	'café'	5	Counts bytes: 'é' is 2 bytes, total 5 bytes
2	CHAR_LENGTH	'café'	4	Counts characters: 'c','a','f','é' = 4 characters
3	END			Query finishes after both functions return values

💡 Both functions return their counts; LENGTH counts bytes, CHAR_LENGTH counts characters

Variable Tracker

Variable	Start	After LENGTH	After CHAR_LENGTH	Final
Input String	'café'	'café'	'café'	'café'
LENGTH Result	NULL	5	5	5
CHAR_LENGTH Result	NULL	NULL	4	4

Key Moments - 2 Insights

Why does LENGTH('café') return 5 but CHAR_LENGTH('café') returns 4?

Because LENGTH counts bytes and 'é' uses 2 bytes in UTF-8, while CHAR_LENGTH counts characters, so it counts 'é' as one character (see execution_table rows 1 and 2).

Will LENGTH and CHAR_LENGTH always return the same number?

No, they differ when the string contains multi-byte characters like accented letters or emojis, as shown in the example with 'café'.

Visual Quiz - 3 Questions

Look at the execution table, what is the output of LENGTH('café')?

A 3

B 4

C 5

D 6

💡 Hint

Check the row where Function is LENGTH and Input String is 'café' in the execution_table.

At which step does CHAR_LENGTH return its value?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Look for the row where Function is CHAR_LENGTH in the execution_table.

If the input string was 'cat' (all ASCII), how would LENGTH and CHAR_LENGTH compare?

A LENGTH would be greater than CHAR_LENGTH

B Both would be equal

C CHAR_LENGTH would be greater than LENGTH

D Both would be zero

💡 Hint

ASCII characters use 1 byte each, so LENGTH and CHAR_LENGTH count the same number.

Concept Snapshot

LENGTH(string) returns the number of bytes in the string.
CHAR_LENGTH(string) returns the number of characters.
They differ when string has multi-byte characters.
Use LENGTH for byte size, CHAR_LENGTH for character count.
Example: LENGTH('café')=5, CHAR_LENGTH('café')=4.

Full Transcript

This lesson shows how LENGTH and CHAR_LENGTH work in SQL. LENGTH counts bytes in a string, so multi-byte characters like 'é' count as more than one. CHAR_LENGTH counts characters, so 'é' counts as one. For example, 'café' has 5 bytes but 4 characters. The execution table shows LENGTH returns 5 and CHAR_LENGTH returns 4 for 'café'. This difference is important when working with strings containing special characters. ASCII strings have equal LENGTH and CHAR_LENGTH. Remember: LENGTH is byte count, CHAR_LENGTH is character count.