PostgreSQL Essential Reference

Map of Functions Grouped by Category

Function	Category
Aggregate functions	AVG COUNT MAX MIN STDDEV SUM VARIANCE
Conversion functions	CAST TO_CHAR TO_DATE TO_NUMBER TO_TIMESTAMP
Geometric functions	AREA BOX CENTER CIRCLE DIAMETER HEIGHT ISCLOSED ISOPEN LENGTH LSEG NPOINTS PATH PCLOSE POINT POLYGON POPEN RADIUS WIDTH
Network functions	ABBREV BROADCAST HOST MASKLEN NETMASK NETWORK TEXT TRUNC
Numerical functions	ABS ACOS ASIN ATAN ATAN2 CBRT CEIL COS COT DEGREES EXP FLOOR LN LOG PI POW or POWER RADIANS RANDOM ROUND SIN SQRT TAN TRUNC
SQL functions	CASE WHEN COALESCE NULLIF
String functions	ASCII CHR INITCAP LENGTH, CHAR_LENGTH,or CHARACTER_LENGTH LOWER LPAD LTRIM OCTET_ POSITION STRPOS RPAD RTRIM SUBSTRING SUBSTR TRANSLATE TRIM UPPER
Time functions ...