SQL String Functions Practice Questions

Split on a delimiter with SPLIT_PART, or slice with SUBSTR and POSITION.

• SUBSTR(text, start, length) is 1-based.
• POSITION('@' IN email) finds where the delimiter is.
• SPLIT_PART(email, '@', 2) returns the second piece in PostgreSQL.

Use LIKE for simple patterns. Use a regular expression when you need character classes or repeats.

• LIKE: % matches any number of characters, _ matches exactly one.
• ILIKE is the case-insensitive version in PostgreSQL.
• Regex in PostgreSQL uses ~ (for example phone ~ '^[0-9]{10}$').

In PostgreSQL, joining any value with NULL using || gives NULL.

• CONCAT treats NULL as an empty string.
• CONCAT_WS(sep, ...) skips NULLs and adds the separator only between real values (shown here).
• Use COALESCE if you want a specific fallback text.