Merge pull request #33 from zbrookle/update_documentation

DOC: Put link to sql_to_ibis rather than in README.md

Author: zbrookle

README.md

@@ -32,77 +32,8 @@ The package currently only supports pandas but there are plans to support dask a
 rapids in the future.
 
 ## SQL Syntax
-The sql syntax for dataframe_sql is as follows:
+The SQL syntax for dataframe_sql is exactly the same as the syntax in *sql_to_ibis*,
+its underlying package:
 
-Select statement:
+You can see the full SQL syntax [here](https://github.com/zbrookle/sql_to_ibis)
 
-```SQL
-SELECT [{ ALL | DISTINCT }]
-    { [ <expression> ] | <expression> [ [ AS ] <alias> ] } [, ...]
-[ FROM <from_item>  [, ...] ]
-[ WHERE <bool_expression> ]
-[ GROUP BY { <expression> [, ...] } ]
-[ HAVING <bool_expression> ]
-```
-
-Set operations:
-
-```SQL
-<select_statement1>
-{UNION [DISTINCT] | UNION ALL | INTERSECT [DISTINCT] | EXCEPT [DISTINCT] | EXCEPT ALL}
-<select_statment2>
-```
-
-Joins:
-
-```SQL
-INNER, CROSS, FULL OUTER, LEFT OUTER, RIGHT OUTER, FULL, LEFT, RIGHT
-```
-
-Order by and limit:
-
-```SQL
-<set>
-[ORDER BY <expression>]
-[LIMIT <number>]
-```
-
-Supported expressions and functions:
-```SQL
-+, -, *, /
-```
-```SQL
-CASE WHEN <condition> THEN <result> [WHEN ...] ELSE <result> END
-```
-```SQL
-SUM, AVG, MIN, MAX
-```
-```SQL
-{RANK | DENSE_RANK} OVER([PARTITION BY (<expresssion> [, <expression>...)])
-```
-```SQL
-CAST (<expression> AS <data_type>)
-```
-*Anything in <> is meant to be some string <br>
-*Anything in [] is optional <br>
-*Anything in {} is grouped together
-
-### Supported Data Types for cast expressions include:
-* VARCHAR, STRING
-* INT16, SMALLINT
-* INT32, INT
-* INT64, BIGINT
-* FLOAT16
-* FLOAT32
-* FLOAT, FLOAT64
-* BOOL
-* DATETIME64, TIMESTAMP
-* CATEGORY
-* OBJECT
-
-*Data types in dataframe SQL support many different name for certain datatypes becuase
-popular SQL data types are not implemented with common names in pandas and other
-dataframe frameworks
-<br>
-**To make this less confusing all data types that are of the same size on the
-backend are grouped together in this list