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The SQL parser to parse cursor.execute(sql, mode='portable') statements has already been written and is available as a standalone module named SQLParserTools. The approach of parsing an SQL statement just to rebuild it again in an abstraction layer function might sound unnecessary but the advantage is that the SQL written in this manner is guaranteed to function in the same way across all web.database databases.
This specification implements what is considered the lowest possible useful SQL feature set which is commonly used and which all databases will support. A balance has had to be made between including useful features and excluding features which only some database engines support. Also no duplication of features has been included. For example BETWEEN can be implemented using > and < operators in the WHERE clause so has not been included but the LIKE operator has.
The specification includes:
A database most often contains one or more tables. Each table is identified by a name (e.g. Customers or Orders). Tables contain records (rows) with data.
Below is an example of a table called Person:
+----------+-----------+--------+-------------+ | LastName | FirstName | Number | DateOfBirth | +----------+-----------+--------+-------------+ | Smith | John | 10 | 1980-01-01 | +----------+-----------+--------+-------------+ | Doe | John | 3 | 1981-12-25 | +----------+-----------+--------+-------------+
The table above contains two records (one for each person) and four columns (LastName, FirstName, Address, and DateOfBirth).
With SQL, we can query a database and have a result set returned.
A query looks like this:
SELECT LastName FROM Person
Gives a result set like this:
+----------+ | LastName | +----------+ | Smith | +----------+ | Doe | +----------+
Note: Some database systems require a semicolon at the end of the SQL statement. web.database does not.
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