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updating a relational database php-29

One thing to note about exec verus query: the first executes a result-less query, and the latter performs a query that returns results.

It is better to use a prepared statement than a query though.

Although SQL is an ANSI/ISO standard, there are different versions of the SQL language.

However, to be compliant with the ANSI standard, they all support at least the major commands (such as SELECT, UPDATE, DELETE, INSERT, WHERE) in a similar manner.

This example database is much like that shown earlier, except that it exercises strict control over inventory and salespeople — both can appear in an invoice, but neither of them can be changed by an invoice creator, with a single exception — the stock item quantities that appear on an invoice are automatically subtracted from the inventory.

Here are the three tables as they appear after the transaction defined in the demonstration file relational_demo.sql: Look carefully at figures 4,5 and 6 (created using JDBClient) — notice that the salespeople table has a key named "salesperson_id", the inventory table has a key named "inventory_id", and the invoice table has two keys with the same names.A relational database solves these problems by strictly ordering the relationship between the levels, thus preventing the entry of a species not appropriate to a given genus, or genus to a family, and so forth.Until recently such an arrangement was dearly wished for but not practical.In a relational database system, this would be managed by adding a single entry to the table for the genus Icterus.From a practical standpoint, what this means is that the task of classification now has the absolute minimum of complexity — one species: one table entry — and all uses of that information automatically follow.RDBMS stands for Relational Database Management System.