1 expression
1.1  = 
1.1  <> 
1.1  < 
1.1  > 
1.1  <= 
1.1  >= 
1.2 (1) 

1.3 expression
1 ( row-value-expression )
1.1  = 
1.1  <> 
1.2 ( row-value-expression )
1 ( fullselect )
1.1  = 
1.1  <> 
1.2 ( row-value-expression )
1 ( row-value-expression )
1.1  = 
1.1  <> 
1.2 ( fullselect )