Shulou(Shulou.com)06/01 Report--

Parallel query: take union, that is, all data

(select deptno from emp)

Union

(select deptno from dept)

Intersection query: take the intersection of two tables, and the result belongs to both An and B.

(select deptno from emp)

Intersect

(select deptno from dept)

Nested queries with poor operations: those that belong to a but not to B. On the other hand, there is no data. The extra one should be written in front.

(select deptno from dept)

Minus

(select deptno from emp)

Description:

Union, which joins two result sets, excluding duplicate rows, and sorts the default rules

Union All, union of two result sets, including duplicate rows, without sorting

Intersect, which intersects two result sets, excluding duplicate rows, and sorts the default rules

Minus, which performs differential operations on two result sets, excluding duplicate rows, and sorts the default rules.

Ceil function

Ceil (n), taking the smallest integer greater than or equal to the value N.

Example: select sal,ceil (sal/100) from emp

Floor function

Floor (n), the largest integer whose value is less than or equal to the value N; the usage is the same as above.

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