You want to create a domain hex_color that stores a 7-character string starting with '#' followed by exactly 6 hexadecimal digits (0-9, A-F, a-f). Which domain definition is correct?
hard📝 Application Q9 of 15
PostgreSQL - Advanced Features
You want to create a domain hex_color that stores a 7-character string starting with '#' followed by exactly 6 hexadecimal digits (0-9, A-F, a-f). Which domain definition is correct?
ACREATE DOMAIN hex_color AS char(6) CHECK (VALUE ~ '^#[0-9A-Fa-f]{6}$');
BCREATE DOMAIN hex_color AS varchar(7) CHECK (VALUE LIKE '#______');
CCREATE DOMAIN hex_color AS varchar(7) CHECK (VALUE ~ '^#[0-9A-Fa-f]{6}$');
DCREATE DOMAIN hex_color AS varchar(7) CHECK (VALUE ~ '^#[0-9]{6}$');
Step-by-Step Solution
Solution:
Step 1: Check base type and length
The string is 7 characters: '#' plus 6 hex digits, so varchar(7) is correct.
Step 2: Verify regex pattern
The regex '^#[0-9A-Fa-f]{6}$' matches '#' followed by exactly 6 hex digits (case insensitive).
Final Answer:
CREATE DOMAIN hex_color AS varchar(7) CHECK (VALUE ~ '^#[0-9A-Fa-f]{6}$'); -> Option C
Quick Check:
Regex matches '#' plus 6 hex digits, length matches [OK]
Quick Trick:Use regex to validate hex color format precisely [OK]
Common Mistakes:
Wrong length in char type
Using LIKE instead of regex
Ignoring case in hex digits
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