Updated the documentation

README.md

@@ -6,3 +6,37 @@ You may wonder why I'm implementing this, since there's already [xsv](https://gi
 
 1. This is the project I'm implementing to learn Rust
 2. The Rust data ecosystem has evolved immensely since xsv was sarted. Now we can add things like SQL commands to filter csv files, or translate results to parquet files.
+
+## Example
+
+```bash
+$ head wine.csv
+Wine,Alcohol,Malic.acid,Ash,Acl,Mg,Phenols,Flavanoids,Nonflavanoid.phenols,Proanth,Color.int,Hue,OD,Proline
+1,14.23,1.71,2.43,15.6,127,2.8,3.06,.28,2.29,5.64,1.04,3.92,1065
+1,13.2,1.78,2.14,11.2,100,2.65,2.76,.26,1.28,4.38,1.05,3.4,1050
+1,13.16,2.36,2.67,18.6,101,2.8,3.24,.3,2.81,5.68,1.03,3.17,1185
+1,14.37,1.95,2.5,16.8,113,3.85,3.49,.24,2.18,7.8,.86,3.45,1480
+1,13.24,2.59,2.87,21,118,2.8,2.69,.39,1.82,4.32,1.04,2.93,735
+1,14.2,1.76,2.45,15.2,112,3.27,3.39,.34,1.97,6.75,1.05,2.85,1450
+1,14.39,1.87,2.45,14.6,96,2.5,2.52,.3,1.98,5.25,1.02,3.58,1290
+1,14.06,2.15,2.61,17.6,121,2.6,2.51,.31,1.25,5.05,1.06,3.58,1295
+1,14.83,1.64,2.17,14,97,2.8,2.98,.29,1.98,5.2,1.08,2.85,1045
+
+$ cat wine.csv  | ./target/release/csvgr sql "select Wine, avg(Alcohol) from this group by Wine" | ./target/release/csvgr print
+shape: (3, 2)
+┌──────┬───────────┐
+│ Wine ┆ Alcohol   │
+│ ---  ┆ ---       │
+│ i64  ┆ f64       │
+╞══════╪═══════════╡
+│ 3    ┆ 13.15375  │
+├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
+│ 1    ┆ 13.744746 │
+├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
+│ 2    ┆ 12.278732 │
+└──────┴───────────┘
+```
+
+## Built standing on the shoulders of giants
+
+None of this would be possible without [Polars](https://github.com/pola-rs/polars)