add readme

README.md

@@ -0,0 +1,27 @@
+# lahmanlite
+`lahmanlite` is a project for creating a SQLite database of baseball statistics
+from [the Lahman database/Baseball Databank](https://seanlahman.com).
+
+A makefile and SQL scripts are provided that can create a database from
+Lahman's CSV files. Ideally, this means that as long as new releases continue,
+(and the structure of the releases is maintained), an up-to-date database can
+be created. I have also done my best to normalize the data, incorporate
+constraints, and correct errors I've found.
+
+## How to use
+Using either `export` or `env`, set the `LAHMANLITE_CSV_DIR` environment
+variable to the directory containing Lahman data, then run `make`. This will
+generate two files:
+* `lahman-raw.db`, a straight import of the CSV data into SQLite.
+* `lahman.db`, a modified version of `lahman-raw.db` with data corrections, key
+  constraints, and additional schema modifications.
+
+If you only want the raw data, run `make lahman-raw.db` instead.
+
+### Corrections
+Many of the corrections are simple in nature, like:
+* correcting obvious typos
+* changing empty cells to NULL
+* deleting duplicated data
+
+See the `sql` directory to view the exact SQL statements run for each table.