Basics

Query on one Table

select column1, column2, column3 as name
from table
where left=right;

Query on one Table with null Condition

select column1, column2, column3 as name
from table
where column is null;

Join

Join of two Tables

select column1, column2, column3 as name
from table1 t1
     join table2 t2 on t2.column=t1.column
where left=right;

Join of three Tables

select column1, column2, column3 as name
from table1 t1
     join table2 t2 on t2.column=t1.column
     join table3 t3 on t3.column=t2.column
where left=right;

Join of four Tables

select column1, column2, column3 as name
from table1 t1
     join table2 t2 on t2.column=t1.column
     join table3 t3 on t3.column=t2.column
     join table4 t4 on t4.column=t3.column
where left=right;

Aggregaton

Aggregation without Grouping

select 
  sum(column) as total,
  avg(column) as mean,
  count(*) as number_of
from table;

Aggregation with Grouping

select column1, column2, sum(column3) as total , count(*) as number_of
from table
group by column1, column2;

Aggregation with Condition on Group Level

select column1, column2, sum(column3) as total , count(*) as number_of
from table
group by column1, column2
having count(*) = 10;

Aggregation with Join

select column1, column2, sum(column3) as total , count(*) as number_of
from table t1
    join table2 t2 on t2.column=t1.column
group by column1, column2
having count(*) = 10;

Subquery

Subquery in Where Part

select column1, column2
from table
where  left = (
  subquery here
);

Subquery in Select Part

select column1, (subquery here)
from table
where left = right;

Subquery in From Part

select column1, column2
from
    table t1
        join
    (subquery here) t2
        on t2.column=t1.column
where left = right;