Use nulls first or nulls last syntax in Oracle sequencing

-Principle

Nulls first and Nulls last are the syntax supported by the Oracle order by, if an expression is specified in order by, the record that represents a null value is ranked at the top (either ASC or DESC) If the expression is specified in the ORDER by Nulls Nulls last indicates that a record of a null value will be ranked at the end (either ASC or DESC) using the following syntax:--always put nulls at the top Select* fromZL_CBQC Order byCb_ld nulls First--always put nulls at the end Select* fromZL_CBQC Order byCb_ld desc nulls Last