cosevadb 0.0.3

Light weight SQL database designed to manage data in csv format

CosevaDB - Comma Separated Values DB

CosevaDB is a light weight SQL database designed to store, retrieve and manage data in csv format.

Targets are,

• Apps that require SQL DB or external DB server
• Apps that need lightweight replacement for under-utilised heavy-weight DBs such as oracle, MySQL
• Those who need a SQL processor and DB to manage existing csv data files

View detailed description on www.github.com/ppml38/cosevadb

Features:

• Written purely in python
• No external dependencies

Its a best practice to organise folders and csv files i.e., Databases and tables in below structure

database_name/
      table_name.csv
      table_header.csv
      ...

And to query the database like below

cosevadb.query("select name from path/to/database_name/table_name.csv, path/to/database_name/table_header.csv where role='Manager' & salary >= 5000")

However it is not mandatory to follow. you can pass the path of any csv file to parse.

How to install

pip install cosevadb

Usage

from cosevadb import cosevadb
cosevadb.query("select name,age from data/passengers.csv,data/header.csv where native='USA'")

Return format

[sqlcode,'<message>',[result list / empty list]]

SQL return codes

SQL Code	Description
1	Empty result set
0	Success with atleast one result
-2	Unexpected character on position <index>
-3	Unexpected character on where clause position <index>
-4	Unsupported operator in where clause
-5	Non numeric operand with arithmatic operator <operator>
-6	Non boolean operand(LHS) with logical operator <operator>
-7	Non boolean operand(RHS) with logical operator <operator>
-8	Operator ! must be followed by =
-9	Unbalanced paranthesis on LHS of operator <operator>
-10	Unbalanced paranthesis on RHS of operator <operator>
-11	No field <fieldname> found in header file
-12	Value for variable <variablename> is missing in atleast one row
-13	Where clause condition returns non-boolean result
-14	Incomplete condition in where clause

Reserved words

Keywords
SELECT
FROM
WHERE

Operators supported

Operator type	Operators
Arithmatic operators	+, -, *, /, %
Comparison operators	>, <, >=, <=, =, !=
Logical operators	&, |

Operator precedence (in order from high to low)

Operator precedence
%
/
*
+
-
<,<=
>,>=
!=
=
&
|

File formats

Comma seperated value(.csv) files.

Instructions

• String values should be within ''
• A file with headers(Comma separated) should be passed along with csv data file
• As of now only select operations implemented
• Comparison operator '=' is used instead of '=='
• Expression evaluation will use BODMAS as you studied in school. i.e., It has individual operator precedence unlike python or java. (ex): '9-7+1' will result '1' where python eval() will return 3

Licence

MIT Licence. Contributions are welcome