SQLite-how to compare two column

friends,

I am doi开发者_如何学Pythonng an Android project in my company, still some small work is remaining, I need your help to complete the task.

The problem is...

I have created two tables in which, table1 has an empty column, for purpose for saving name...

The table2 has a list of names, the objective is only the names from this list should be should be saved in the table1's empty column other than that it shouldn't accept any of the name typed manually.

You appear to want to make the list of names a validation: if the user wishes to save a name to table1, the name must already exist in table2.

Typically this would be done as in the following example, in which only the products listed in PRIZEPRODUCTS can be entered into PRIZEWINNERS table: someone could not win a Boat, for example, given the data below:

           PRIZEPRODUCTS
           id
           productname

           1|TV
           2|iPad
           3|backpack



           PRIZEWINNERS
           id
           productid
           winner


           ALTER TABLE PRIZEWINNERS
           ADD CONSTRAINT PRIZEWINNERS_PRIZEPRODUCTS_FK
           FOREIGN KEY(productid) REFERENCES PRIZEPRODUCTS(id)

SQLite doesn't create the foreign key using ALTER TABLE but as part of the create-table statement. See here for the syntax. For enabling foreign key support in Android (2.2), see here.

Now, you can establish the foreign key on the [productname] column if [productname] were the key of PRIZEPRODUCTS. In other words, you could make person-name the key of the table rather than having a PersonID. But if that name is changed in the validation table, it can break the foreign key relationship, unless ON UPDATE CASCADE is enabled, but I am not sure if this is supported in Android.

I hope below query will work for you.

insert into table1(name) values (select name from table2 where id=?).

Thanks.