minglotus的专栏

MEANING: SOME compares a value to each value in a list or results from a query and evaluates to true if the result of an inner query contains at least one row. SOME must match at least one row in the

delete, insert, modify these operations which may alter the contents of a table have to be done before any change to the table happens. insert insert into table values(column_v1, column_v2, column_v3

(natural) join (natural) join … using … join…on difference between natural join using and join on in natural join, column specified by using appears only once, but in join on, it appears twice. join

correlated subquery(相关子查询) correlation name from an outer query used in a subquery in a where clause scoping rule for correlation query 1)It’s only legal to use correlation names defined in the subq

WA: select Customers.Name as Customers from Customers where Customers.Name not in (select Customers.Name from Customers join Orders on Customers.Id = Orders.CustomerId) ; AC: select Customers.Name a

Select out of following the code which uses a JOIN to show a list of all the departments and number of employed teachers WA:  SELECT dept.name, COUNT(teacher.name) FROM teacher JOIN dept ON dept.