4.24 Database Date function table connection processing string

（1) Date function1, year--take the year out2, DateAdd (Day5 '1999-02-27'）--in the date basically added 5 days no one AH and then output3, datedif--How many days do two dates differ4, weekday--string form, the day of the week in one weeks5, week--int type Time6, getdate--Get system Time7, print getdate ()--gets the system current time return value for the datetime type (2)1, any ()--greater than any one value2, all ()--is greater than all values (3) Union--A table join joins two tables with equal data types (4)1，SelectLeft ()--intercept from left to right2，SelectRight ()--intercept from right to left3,SelectLower ()--Convert to lowercase4，SelectUpper ()--Convert to uppercase

4.24 Database Date function table connection processing string