PostgreSQL----Any/some&&all

I. Any/some

WHERE expression operator any (subquery)
WHERE expression operator SOME (subquery)

In fact, any and some are equally effective here, the result set of a subquery can only be a field, the left expression uses operator to perform a comparison operation on each row of the result set, and if one of the results is ' true ', the expression result is ' true ' if the result of the comparison is all ' False ' expression result is ' false '.

> Any is larger than a value in the subquery result

< any is less than one of the values in the subquery results

>= any is greater than or equal to a value in the subquery result

<= any is less than or equal to one of the values in the subquery result

= Any equals a value in the subquery result, which is equivalent to the in

！ = Any is not equal to one of the values in the subquery result

Example 1. Query the Tbl_insert table, if field A is greater than the value in a row of table Tbl_test field F

Test=#Select *  fromTbl_insertwhereA>  any(SelectF fromtbl_test); A|B|C---+---+------- 2 | 2 |  A 3 | 3 |  - 4 | 4 |  - 5 | 5 | Wuyi 6 | 6 | 1 6 | 6 |  A 6 | 6 | 661 7 | 7 | 3%1 8 | 8 | 3%_1 8 | 8 |3_%_1 7 | 7 |ABC7 | 7 |ABc7 | 7 |ABC ( -Rows

Two. All

WHERE expression operator All (subquery)

In the same subquery, you can still return only one field, and the result of each row of the subquery results in a "true" expression is ' true ', otherwise ' FALSE '.

> All is larger than all values in the subquery results

< All is smaller than all values in the subquery results

>= all is greater than or equal to all values in the subquery result

<= all is less than or equal to all values in subquery results

= all equals all values in the subquery result (unless the subquery results are all equal, so it doesn't really make sense)

！ = All is not equal to any one of the values in the subquery result, equal to

Example 1. Querying the largest row of a Tbl_insert table

Test=#Select *  fromTbl_insertwhereA=(Select Max(a) fromTbl_insert); A|B|C---+---+------- 8 | 8 | 3%_1 8 | 8 |3_%_1(2rows) Test=#Select *  fromTbl_insertwhereA>=  All(SelectA fromTbl_insert); A|B|C---+---+------- 8 | 8 | 3%_1 8 | 8 |3_%_1(2Rows

Example 2. Querying the smallest row of a Tbl_insert table

Test=#Select *  fromTbl_insertwhereA<=  All(SelectA fromTbl_insert); A|B|C---+---+---- 1 | 1 |  One(1row) test=#Select *  fromTbl_insertwhereA=(Select min(a) fromTbl_insert); A|B|C---+---+---- 1 | 1 |  One(1Row

PostgreSQL----Any/some&&all