SQL Statement - UPDATE

Update data with new value
UPDATE tablename SET fieldname1 = values, fieldname2 = values WHERE condition

Update data with value in another table
UPDATE tablename1 SET tablename1.fieldname=tablename2.fieldname FROM tablename2 WHERE condition

SQL Statement - SELECT

Select data from 1 table
SELECT * FROM TableNames

Select data from 2 or more tables
SELECT table1.*, table2.* FROM table1,table2 WHERE table1.field1=table2.field1

Append 2 tables
SELECT * FROM table1
UNION
SELECT * FROM table2

Select data which is not exists in another table
SELECT * FROM table1 WHERE NOT EXISTS (SELECT * FROM table2 WHERE table1.field1=table2.field1)