PostgreSQL.get_primary_keys

PostgreSQL.get_primary_keys(table_name, schema_name=None, names_only=True)

Get the primary keys of a table.

Parameters:

• table_name (str) – name of a table

• schema_name (str | None) – name of a schema, defaults to None

• names_only (bool) – whether to return only the names of the primary keys, defaults to True

Returns:

primary key(s) of the given table

Return type:

list | pandas.DataFrame

Examples:

>>> from pyhelpers.dbms import PostgreSQL
>>> from pyhelpers._cache import example_dataframe

>>> testdb = PostgreSQL('localhost', 5432, 'postgres', database_name='testdb')
Password (postgres@localhost:5432): ***
Creating a database: "testdb" ... Done.
Connecting postgres:***@localhost:5432/testdb ... Successfully.

>>> dat = example_dataframe()
>>> dat
            Longitude   Latitude
City
London      -0.127647  51.507322
Birmingham  -1.902691  52.479699
Manchester  -2.245115  53.479489
Leeds       -1.543794  53.797418

>>> tbl_name = 'test_table'

>>> testdb.import_data(data=dat, table_name=tbl_name, index=True, verbose=True)
To import data into "public"."test_table" at postgres:***@localhost:5432/postgres
? [No]|Yes: yes

>>> pri_keys = testdb.get_primary_keys(table_name=tbl_name)
>>> pri_keys
[]

>>> testdb.add_primary_keys(primary_keys='City', table_name=tbl_name)

The “test_table” is illustrated in Fig. 14 below:

Fig. 14 The table “test_table” (with a primary key) in the database.

>>> pri_keys = testdb.get_primary_keys(table_name=tbl_name)
>>> pri_keys
['City']
>>> pri_keys = testdb.get_primary_keys(table_name=tbl_name, names_only=False)
>>> pri_keys
  key_column data_type
0       City      text

>>> # Delete the database "testdb"
>>> testdb.drop_database(verbose=True)
To drop the database "testdb" from postgres:***@localhost:5432
? [No]|Yes: yes
Dropping "testdb" ... Done.