Help Delete Query (1 Viewer)

[GaDauBac]

I have 1 database (attachment)
- I can't run Delete query to manually delete specified fields
Please everyone help me. Thank you very much!

 

[arnelgp]

there is no attachment

 

[GaDauBac]

there is no attachment

Attached file here. Sorry for the sudden power outage

 

[arnelgp]

check and test.

 

[GaDauBac]

check and test.

I still want to keep the relationship like this

 

[Pat Hartman]

The schema is incorrect. It violates second normal form. MaKH does not belong in tb2_ChiTietHopDong. You would obtain the MaKH value by joining to tbl2_ThongTinHopDong.

You didn't explain what exactly your problem was but when you have two related tables in a query and you try to delete a row (you CANNOT delete a column, you only delete rows), it is the "child" table that you delete from NOT the parent table. If you want to delete a row from a parent table based on a value in the child table, you MUST have cascade delete specified since you obviously cannot delete a parent that has child record without it AND you need to use a sub query to identify the row since you can only delete child rows from a query with a join.

 

[GaDauBac]

The schema is incorrect. It violates second normal form. MaKH does not belong in tb2_ChiTietHopDong. You would obtain the MaKH value by joining to tbl2_ThongTinHopDong.

You didn't explain what exactly your problem was but when you have two related tables in a query and you try to delete a row (you CANNOT delete a column, you only delete rows), it is the "child" table that you delete from NOT the parent table. If you want to delete a row from a parent table based on a value in the child table, you MUST have cascade delete specified since you obviously cannot delete a parent that has child record without it AND you need to use a sub query to identify the row since you can only delete child rows from a query with a join.

Thank you! I edited it again, but when I delete the record in tbl2_ThongTinHopDong, I still get an error. I'm still studying with you.

 

[Pat Hartman]

You didn't remove MaKH from the rightmost table but that isn't causing the problem. It is just a design flaw.

You have RI enforced so you CANNOT delete rows from the middle table if there are rows in the right side table unless you allow Cascade Delete.