Improves README by adding examples

README.md

@@ -4,13 +4,44 @@
 
  Only the first statement is supported by Adwords API, the others are proposed by the AWQL command line tool.
 
-## Example
+## Examples
 
- ```go
-q := `SELECT CampaignName FROM CAMPAIGN_PERFORMACE_REPORT ORDER BY 1 LIMIT 5\G`
-stmts, _ := NewParser(strings.NewReader(q)).Parse()
-if stmt, ok := stmts[0].(SelectStmt); ok {
-    fmt.Println(stmt.OrderList()[0].ColumnName)
-    // Output: CampaignName
+### Unknown single statement.
+
+```go
+q := `SELECT CampaignId, CampaignName FROM CAMPAIGN_PERFORMANCE_REPORT;`
+stmt, _ := awql.NewParser(strings.NewReader(q)).ParseRow()
+if stmt, ok := stmt.(awql.SelectStmt); ok {
+    fmt.Println(stmt.SourceName())
+    // Output: CAMPAIGN_PERFORMANCE_REPORT
+}
+```
+
+### Select statement.
+
+```go
+q := `SELECT AdGroupName FROM ADGROUP_PERFORMANCE_REPORT;`
+stmt, _ := awql.NewParser(strings.NewReader(q)).ParseSelect()
+fmt.Printf("Gets the column named %v from %v.\n", stmt.Columns()[0].Name(), stmt.SourceName())
+// Output: Gets the column named AdGroupName from ADGROUP_PERFORMANCE_REPORT.
+```
+
+### Multiple statements.
+
+```go
+q := `SELECT CampaignName FROM CAMPAIGN_PERFORMANCE_REPORT ORDER BY 1 LIMIT 5\GDESC ADGROUP_PERFORMANCE_REPORT AdGroupName;`
+stmts, _ := awql.NewParser(strings.NewReader(q)).Parse()
+for _, stmt := range stmts {
+    switch stmt.(type) {
+    case awql.SelectStmt:
+        fmt.Println(stmt.(awql.SelectStmt).OrderList()[0].Name())
+    case awql.DescribeStmt:
+        fmt.Println(stmt.(awql.DescribeStmt).SourceName())
+        fmt.Println(stmt.(awql.DescribeStmt).Columns()[0].Name())
+    }
 }
- ```
+// Output:
+// CampaignName
+// ADGROUP_PERFORMANCE_REPORT
+// AdGroupName
+```