ftrotter / querpy

A Query class to make building SQL strings in Python as painless as possible.

querpy - to make building SQL strings in Python as painless as possible

The Query class is intended to provide a high level interface for building/editing SQL query strings.

This library should now support python 3.

Example usage:

    >>> from querpy import Query
    >>> new_query = Query()
    >>> new_query.f += 'ex_db.dbo.ex_table tbl'
    >>> new_query.s += ['col1', 'col2', 'col3']  # can take lists
    >>> new_query.s += 'col4'  # can take single strings
    >>> new_query.w += 'col1 = 1'  # can also take a list (separated by AND)
    >>> new_query.w |= 'col2 IS NULL'  # handles &= and |= operators
    >>> print new_query
    SELECT
        col1,
        col2,
        col3,
        col4
      FROM
        ex_db.dbo.ex_table tbl
      WHERE
        col1 = 1 
          OR col2 IS NULL
    
	>>> new_query  # also prints full query
    SELECT
        col1,
        col2,
        col3,
        col4
      FROM
        ex_db.dbo.ex_table tbl
      WHERE
        col1 = 1 
          OR col2 IS NULL

The Query class avoids redundancy for similar queries by allowing you to modify a single component at a time:

    >>> new_query.s.clear()  # clear SELECT component
    >>> new_query.s += 'col1'
    >>> new_query
    SELECT
        col1
      FROM
        ex_db.dbo.ex_table tbl
      WHERE
        col1 = 1 
          OR col2 IS NULL

Another way to edit the SELECT clause is to use indexing:

    >>> new_query.s[0] = 'col2'
    >>> print new_query.s  # printing the component shows indices
    index: item
    0: 'col2'

Suppose you want to extend your query by joining to another table and adding columns from this table:

    >>> new_query.j += 'ex_db.dbo.new_tbl nt ON tbl.id = nt.id'
    >>> new_query.s += 'nt.id'
    >>> new_query
    SELECT
        col1,
        nt.id
      FROM
        ex_db.dbo.ex_table tbl
          JOIN ex_db.dbo.new_tbl nt ON tbl.id = nt.id
      WHERE
        col1 = 1 
          OR col2 IS NULL

While this works, we are returning to the land of long strings. We can do the same thing (n.b. we'll LEFT JOIN this time) using the Query.build_join helper function to make the join step more readable and modular:

    >>> new_query.j.clear()
    >>> new_query.join_type = 'LEFT'
    >>> new_query.j += Query.build_join('ex_db.dbo.new_tbl nt', 'tbl.id', 'nt.id', 'tbl.city', 'nt.city')
    >>> new_query.join_type = ''  # set back to regular join
    >>> new_query
    SELECT
        col1,
        nt.id
      FROM
        ex_db.dbo.ex_table tbl
          LEFT JOIN ex_db.dbo.new_tbl nt ON tbl.id = nt.id AND tbl.city = nt.city
      WHERE
        col1 = 1 
          OR col2 IS NULL

When your query string is ready to be passed to the function that will execute the query, simply pass it using statement (without the pretty print fluff):

    >>> new_query.statement
    SELECT col2, nt.id FROM ex_db.dbo.ex_table tbl LEFT JOIN ex_db.dbo.new_tbl nt ON tbl.id = nt.id AND tbl.city = nt.city WHERE col1 = 1 OR col2 IS NULL

You can also prepend a CREATE TABLE <> AS to the SQL

    >>> new_query.j += 'ex_db.dbo.new_tbl nt ON tbl.id = nt.id'
    >>> new_query.s += 'nt.id'
    >>> new_query.g += 'col1'
    >>> new_query.l += ' 10, 100' 
    >>> new_query.ci += ' db_name.tbl_name ' 
    >>> new_query
    CREATE TABLE db_name.tbl_name AS 
    SELECT
        col1,
        nt.id
      FROM
        ex_db.dbo.ex_table tbl
          JOIN ex_db.dbo.new_tbl nt ON tbl.id = nt.id
      WHERE
        col1 = 1 
          OR col2 IS NULL
      GROUP BY 
        col1
      LIMIT 10, 100

Suppose you want to extend your query by joining to another table and adding columns from this table:

NOTE: the SQL constructed is not validated.