1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
.. currentmodule:: Orange.data.sql.table
########################
SQL table (``data.sql``)
########################
.. autoclass:: Orange.data.sql.table.SqlTable
:members:
:special-members:
:obj:`SqlTable` represents a table with the data which is stored in the
database. Besides the inherited attributes, the object stores a connection
to the database and row filters.
Constructor connects to the database, infers the variable types from the
types of the columns in the database and constructs the corresponding
domain description. Discrete and continuous variables are put among
attributes, and string variables are meta attributes. The domain does not
have a class.
:obj:`SqlTable` overloads the data access methods for random access to
rows and for iteration (`__getitem__` and `__iter__`). It also provides
methods for fast computation of basic statistics, distributions and
contingency matrices, as well as for filtering the data. Filtering the
data returns a new instance of :obj:`SqlTable`. The new instances however
differs only in that an additional filter is added to the row_filter.
All evaluation is lazy in the sense that most operations just modify the
domain and the list of filters. These are used to construct an SQL query
when the data is actually needed, for instance to retrieve a data row or
compute a distribution of values for a certain column.
.. attribute:: connection
The object that holds the database connection. An instance of a class
compatible with Python DB API 2.0.
.. attribute:: host
The host name of the database server
.. attribute:: database
The name of the database
.. attribute:: table_name
The name of the table in the database
.. attribute:: row_filters
A list of filters that are applied when constructing the query. The
filters in the should have a method `to_sql`. Module
:obj:`Orange.data.sql.filter` contains classes derived from filters in
:obj:`Orange.data.filter` with the appropriate implementation of the
method.
|
