Relational databases and queries

Computer ScienceFiles, Storage & DatabasesAges 16–17

Two tables, HOC_SINH and LOP, are linked by the foreign key MaLop pointing to the primary key MaLop of the LOP table. Students build a query with a set of selectors: which table to use, whether to join the two tables, what the filter condition is, which column to sort by, and how many rows to return. The program generates the matching SQL statement and runs it live on the data, so changing a condition instantly changes the result table; clicking a row shows which row of the other table it was joined with.