Adding upstream version 20.4.0.upstream/20.4.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/README.md b/README.md
index d5d3d29..70ce7af 100644
--- a/README.md
+++ b/README.md
@@ -4,11 +4,11 @@ SQLGlot is a no-dependency SQL parser, transpiler, optimizer, and engine. It can
 
 It is a very comprehensive generic SQL parser with a robust [test suite](https://github.com/tobymao/sqlglot/blob/main/tests/). It is also quite [performant](#benchmarks), while being written purely in Python.
 
-You can easily [customize](#custom-dialects) the parser, [analyze](#metadata) queries, traverse expression trees, and programmatically [build](#build-and-modify-sql) SQL.
+You can easily [customize](#custom-dialects) the parser, [analyze](#metadata) queries, traverse expression trees, and programmatically [build](#build-and-modify-sql) SQL. 
 
 Syntax [errors](#parser-errors) are highlighted and dialect incompatibilities can warn or raise depending on configurations. However, it should be noted that SQL validation is not SQLGlot’s goal, so some syntax errors may go unnoticed.
 
-Learn more about the SQLGlot API in the [documentation](https://sqlglot.com/).
+Learn more about SQLGlot in the API [documentation](https://sqlglot.com/) and the expression tree [primer](https://github.com/tobymao/sqlglot/blob/main/posts/ast_primer.md).
 
 Contributions are very welcome in SQLGlot; read the [contribution guide](https://github.com/tobymao/sqlglot/blob/main/CONTRIBUTING.md) to get started!
 
@@ -176,6 +176,8 @@ for table in parse_one("SELECT * FROM x JOIN y JOIN z").find_all(exp.Table):
     print(table.name)
 ```
 
+Read the [ast primer](https://github.com/tobymao/sqlglot/blob/main/posts/ast_primer.md) to learn more about SQLGlot's internals.
+
 ### Parser Errors
 
 When the parser detects an error in the syntax, it raises a ParseError: