PostgreSQL.get_primary_keys

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

Retrieve the primary keys of a table.

Parameters:

• table_name (str) – Name of the table.

• schema_name (str | None) – Name of the 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(database_name='testdb', verbose=True)
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 Figure 19 below:

Figure 19 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.