Postgresql Common Commands

The introduction recently collated some of the most common commands for PostgreSQL, for reference 1 only. Common commands:

# time Word Fu timestampSelectExtract (Epoch fromDate'2018-04-11 23:59:59')); #1523404800# Timestamp to time stringSelectDate (To_timestamp (1523404800) # Timestamp to stringSelectTo_char (To_timestamp (1523404800),'YYYY-MM-DD HH24:MI:SS') # Convert numeric typeCAST(T3.userid as text) # int NUMERIC VARCHAR can also

# Default Value
　　coalesce(null, 1); # 1

2. Common numeric functions

AVG () returns the average of a column

COUNT () returns the number of rows in a column

Max () returns the maximum value of a column

MIN () returns the minimum value of a column

Sums () returns the sum of the values of a column

3. Commonly used String functions

Lengtah (s) calculates the string length

CONCAT (s1,s2,......) string merge function

Letrim (s)/rtrim (s)/trim (s) Delete string space function

Replace (S,S1,S2) string substitution function

SUBSTRING (s,n,len) Get substring function

4. Commonly used date and time functions

EXTRACT (type from D) Get date specified value function

Current_date getting the current date function

Current_time Get current time

Postgresql Common Commands