I. Connecting queries within a connection
Select a. field, B. field from table 1 A, table 2 B where a. field =b. Fields and ...
Two. DML Data Manipulation language
1. Add insert INTO values
1-insert into table name values (a list of values corresponding to all field one by one)
2-insert into table name (field list) values (a list that corresponds to the field list one by one)
3-insert into table name select corresponding field list from source table name where condition
4-insert into table name (field list) Select corresponding field list from source table name where condition
2. Delete delete
1-Full table Delete: Delete from table name
2-Select Delete: Delete from table name where condition
3. Change the update set
1-Full Table modification: Update table name set field name = new Value,...
2-Select Modify: Update table name set field name = new value,... WHERE condition
Three. Aggregation functions of built-in functions
1.COUNT Statistics Record Bar number
2.SUM () Total statistics
3.AVG statistical average
4.MAX returns the maximum value
5.MIN returns the minimum value
6. Features
1-can be used alone in a query or in conjunction with a group
2-If the field contents are null, the statistics are ignored
Data store--sqlite Statement of DML data manipulation language and aggregation functions of built-in functions