diff --git a/docs/chapter1/section4/1_sql.md b/docs/chapter1/section4/1_sql.md
index 44600ea7..e18de97a 100644
--- a/docs/chapter1/section4/1_sql.md
+++ b/docs/chapter1/section4/1_sql.md
@@ -14,7 +14,7 @@ mysql> SHOW DATABASES;
 
 以下のように出力されるはずです。
 
-```txt
+```html
 +--------------------+
 | Database           |
 +--------------------+
@@ -44,7 +44,7 @@ mysql> USE world;
 mysql> SHOW TABLES;
 ```
 
-```txt
+```html
 +-----------------+
 | Tables_in_world |
 +-----------------+
@@ -69,7 +69,7 @@ mysql> DESCRIBE city;
 mysql> SHOW COLUMNS FROM city;
 ```
 
-```txt
+```html
 +-------------+----------+------+-----+---------+----------------+
 | Field       | Type     | Null | Key | Default | Extra          |
 +-------------+----------+------+-----+---------+----------------+
@@ -96,7 +96,7 @@ https://dev.mysql.com/doc/refman/8.0/ja/getting-information.html
 mysql> SELECT Name, Population FROM city;
 ```
 
-```txt
+```html
 +-----------------------------------+------------+
 | Name                              | Population |
 +-----------------------------------+------------+
@@ -123,7 +123,7 @@ https://dev.mysql.com/doc/refman/8.0/ja/select.html
 mysql> SELECT * FROM city;
 ```
 
-```txt
+```html
 +------+-----------------------------------+-------------+----------------------+------------+
 | ID   | Name                              | CountryCode | District             | Population |
 +------+-----------------------------------+-------------+----------------------+------------+
@@ -148,7 +148,7 @@ mysql> SELECT * FROM city;
 mysql> SELECT * FROM city LIMIT 5;
 ```
 
-```txt
+```html
 +----+----------------+-------------+---------------+------------+
 | ID | Name           | CountryCode | District      | Population |
 +----+----------------+-------------+---------------+------------+
@@ -169,7 +169,7 @@ mysql> SELECT * FROM city LIMIT 5;
 mysql> SELECT * FROM city LIMIT 5 OFFSET 10;
 ```
 
-```txt
+```html
 +----+-----------+-------------+---------------+------------+
 | ID | Name      | CountryCode | District      | Population |
 +----+-----------+-------------+---------------+------------+
@@ -190,7 +190,7 @@ mysql> SELECT * FROM city LIMIT 5 OFFSET 10;
 mysql> SELECT * FROM city WHERE Population >= 8000000;
 ```
 
-```txt
+```html
 +------+-------------------+-------------+------------------+------------+
 | ID   | Name              | CountryCode | District         | Population |
 +------+-------------------+-------------+------------------+------------+
@@ -212,7 +212,7 @@ mysql> SELECT * FROM city WHERE Population >= 8000000;
 mysql> SELECT * FROM city WHERE CountryCode = "JPN" AND Population > 5000000;
 ```
 
-```txt
+```html
 +------+-------+-------------+----------+------------+
 | ID   | Name  | CountryCode | District | Population |
 +------+-------+-------------+----------+------------+
@@ -229,7 +229,7 @@ mysql> SELECT * FROM city WHERE CountryCode = "JPN" AND Population > 5000000;
 SELECT * FROM city WHERE Population >= 8000000 ORDER BY Population DESC;
 ```
 
-```txt
+```html
 +------+-------------------+-------------+------------------+------------+
 | ID   | Name              | CountryCode | District         | Population |
 +------+-------------------+-------------+------------------+------------+
@@ -258,7 +258,7 @@ https://dev.mysql.com/doc/refman/8.0/ja/sorting-rows.html
 mysql> SELECT * FROM city WHERE District IN ("Kagawa", "Tokushima", "Ehime", "Kochi");
 ```
 
-```txt
+```html
 +------+-----------+-------------+-----------+------------+
 | ID   | Name      | CountryCode | District  | Population |
 +------+-----------+-------------+-----------+------------+
@@ -286,7 +286,7 @@ https://dev.mysql.com/doc/refman/8.0/ja/comparison-operators.html#operator_in
 mysql> DESCRIBE countrylanguage;
 ```
 
-```txt
+```html
 +-------------+---------------+------+-----+---------+-------+
 | Field       | Type          | Null | Key | Default | Extra |
 +-------------+---------------+------+-----+---------+-------+
@@ -304,7 +304,7 @@ mysql> DESCRIBE countrylanguage;
 mysql> SELECT country.Name, countrylanguage.Language FROM country JOIN countrylanguage ON country.Code = countrylanguage.CountryCode WHERE countrylanguage.Language = "Chinese";
 ```
 
-```txt
+```html
 +--------------------------+----------+
 | Name                     | Language |
 +--------------------------+----------+
@@ -348,7 +348,7 @@ https://dev.mysql.com/doc/refman/8.0/ja/join.html
 mysql> SELECT Name, District AS Prefecture FROM city WHERE CountryCode = "JPN";
 ```
 
-```txt
+```html
 +---------------------+------------+
 | Name                | Prefecture |
 +---------------------+------------+
@@ -388,7 +388,7 @@ https://dev.mysql.com/doc/refman/8.0/ja/problems-with-alias.html
 mysql> SELECT COUNT(*) FROM city WHERE CountryCode = "JPN";
 ```
 
-```txt
+```html
 +----------+
 | count(*) |
 +----------+
@@ -408,7 +408,7 @@ https://dev.mysql.com/doc/refman/8.0/ja/aggregate-functions.html#function_count
 SELECT CountryCode, COUNT(*) FROM city GROUP BY CountryCode;
 ```
 
-```txt
+```html
 +-------------+----------+
 | CountryCode | COUNT(*) |
 +-------------+----------+
@@ -444,7 +444,7 @@ mysql> INSERT INTO city (Name, CountryCode, District, Population) VALUES ("oooka
 mysql> SELECT * FROM city ORDER BY ID DESC LIMIT 1;
 ```
 
-```txt
+```html
 +------+-----------+-------------+----------+------------+
 | ID   | Name      | CountryCode | District | Population |
 +------+-----------+-------------+----------+------------+
@@ -465,7 +465,7 @@ mysql> UPDATE city SET Population = 9999 WHERE ID = 4080;
 mysql> SELECT * FROM city WHERE ID = 4080;
 ```
 
-```txt
+```html
 +------+-----------+-------------+----------+------------+
 | ID   | Name      | CountryCode | District | Population |
 +------+-----------+-------------+----------+------------+
@@ -491,7 +491,7 @@ mysql> DELETE FROM city WHERE ID = 4080;
 mysql> SELECT * FROM city WHERE ID = 4080;
 ```
 
-```txt
+```html
 Empty set (0.00 sec)
 ```
 
diff --git a/docs/chapter1/section4/2_sql_exercise.md b/docs/chapter1/section4/2_sql_exercise.md
index 0a7ecec0..43b95766 100644
--- a/docs/chapter1/section4/2_sql_exercise.md
+++ b/docs/chapter1/section4/2_sql_exercise.md
@@ -17,7 +17,7 @@ SELECT * FROM country WHERE Name = "Japan";
 
 **出力**
 
-```txt
+```html
 +------+-------+-----------+--------------+-------------+-----------+------------+----------------+------------+------------+--------------+-------------------------+-------------+---------+-------+
 | Code | Name  | Continent | Region       | SurfaceArea | IndepYear | Population | LifeExpectancy | GNP        | GNPOld     | LocalName    | GovernmentForm          | HeadOfState | Capital | Code2 |
 +------+-------+-----------+--------------+-------------+-----------+------------+----------------+------------+------------+--------------+-------------------------+-------------+---------+-------+
@@ -40,7 +40,7 @@ SELECT * FROM country WHERE IndepYear <= 0;
 
 **出力**
 
-```txt
+```html
 +------+----------+-----------+----------------+-------------+-----------+------------+----------------+------------+------------+--------------+-------------------------+----------------+---------+-------+
 | Code | Name     | Continent | Region         | SurfaceArea | IndepYear | Population | LifeExpectancy | GNP        | GNPOld     | LocalName    | GovernmentForm          | HeadOfState    | Capital | Code2 |
 +------+----------+-----------+----------------+-------------+-----------+------------+----------------+------------+------------+--------------+-------------------------+----------------+---------+-------+
@@ -65,7 +65,7 @@ SELECT Name, Population FROM country WHERE Continent = "Asia" ORDER BY Populatio
 
 **出力**
 
-```txt
+```html
 +------------+------------+
 | Name       | Population |
 +------------+------------+
@@ -92,7 +92,7 @@ SELECT * FROM country ORDER BY Population DESC LIMIT 5 OFFSET 10;
 
 **出力**
 
-```txt
+```html
 +------+-------------+---------------+-----------------+-------------+-----------+------------+----------------+------------+------------+-------------+----------------------+-------------------------+---------+-------+
 | Code | Name        | Continent     | Region          | SurfaceArea | IndepYear | Population | LifeExpectancy | GNP        | GNPOld     | LocalName   | GovernmentForm       | HeadOfState             | Capital | Code2 |
 +------+-------------+---------------+-----------------+-------------+-----------+------------+----------------+------------+------------+-------------+----------------------+-------------------------+---------+-------+
@@ -119,7 +119,7 @@ SELECT COUNT(*) AS Japanese FROM countrylanguage WHERE Language = "Japanese";
 
 **出力**
 
-```txt
+```html
 +----------+
 | Japanese |
 +----------+
@@ -142,7 +142,7 @@ SELECT Continent, COUNT(*) FROM country GROUP BY Continent;
 
 **出力**
 
-```txt
+```html
 +---------------+----------+
 | Continent     | COUNT(*) |
 +---------------+----------+
@@ -173,7 +173,7 @@ SELECT country.Name AS Country, city.Name AS Capital FROM country JOIN city ON c
 
 **出力**
 
-```txt
+```html
 +---------------------------------------+------------------------------------+
 | Country                               | Capital                            |
 +---------------------------------------+------------------------------------+
@@ -212,7 +212,7 @@ SELECT * FROM country WHERE Continent IN ("North America", "South America");
 
 **出力**
 
-```txt
+```html
 +------+----------------------------------+---------------+-----------------+-------------+-----------+------------+----------------+------------+------------+-------------------------------------+----------------------------------------------+--------------------------------------+---------+-------+
 | Code | Name                             | Continent     | Region          | SurfaceArea | IndepYear | Population | LifeExpectancy | GNP        | GNPOld     | LocalName                           | GovernmentForm                               | HeadOfState                          | Capital | Code2 |
 +------+----------------------------------+---------------+-----------------+-------------+-----------+------------+----------------+------------+------------+-------------------------------------+----------------------------------------------+--------------------------------------+---------+-------+
@@ -254,7 +254,7 @@ SELECT * FROM country WHERE Name = "traP";
 
 **出力**
 
-```txt
+```html
 +------+------+-----------+--------------+-------------+-----------+------------+----------------+------+--------+-----------+-------------------------+-------------+---------+-------+
 | Code | Name | Continent | Region       | SurfaceArea | IndepYear | Population | LifeExpectancy | GNP  | GNPOld | LocalName | GovernmentForm          | HeadOfState | Capital | Code2 |
 +------+------+-----------+--------------+-------------+-----------+------------+----------------+------+--------+-----------+-------------------------+-------------+---------+-------+
@@ -285,7 +285,7 @@ SELECT * FROM country WHERE Code = "TRP";
 
 **出力**
 
-```txt
+```html
 +------+------+-----------+--------------+-------------+-----------+------------+----------------+------+--------+-----------+-------------------------+-------------+---------+-------+
 | Code | Name | Continent | Region       | SurfaceArea | IndepYear | Population | LifeExpectancy | GNP  | GNPOld | LocalName | GovernmentForm          | HeadOfState | Capital | Code2 |
 +------+------+-----------+--------------+-------------+-----------+------------+----------------+------+--------+-----------+-------------------------+-------------+---------+-------+
@@ -314,7 +314,7 @@ SELECT * FROM country WHERE Code = "TRP";
 
 **出力**
 
-```txt
+```html
 Empty set (0.00 sec)
 ```
 
@@ -336,7 +336,7 @@ SELECT country.Name, city.Name FROM country LEFT JOIN city ON country.Code = cit
 
 **出力**
 
-```txt
+```html
 +----------------------------------------------+-----------------------------------+
 | Name                                         | Name                              |
 +----------------------------------------------+-----------------------------------+
@@ -376,7 +376,7 @@ SELECT RANK() OVER (ORDER BY Population DESC) AS Ranking, Name, Population FROM
 
 **出力**
 
-```txt
+```html
 +---------+--------------------+------------+
 | Ranking | Name               | Population |
 +---------+--------------------+------------+
@@ -412,7 +412,7 @@ SELECT Name, Continent, Region, Population FROM country WHERE Code = (SELECT Cou
 
 **出力**
 
-```txt
+```html
 +---------+-----------+----------------+------------+
 | Name    | Continent | Region         | Population |
 +---------+-----------+----------------+------------+
@@ -442,7 +442,7 @@ ORDER BY Speakers DESC LIMIT 10;
 
 **出力**
 
-```txt
+```html
 +---------+------------+------------------+
 | Ranking | Language   | Speakers         |
 +---------+------------+------------------+
diff --git a/docs/chapter1/section4/3_go_and_db.md b/docs/chapter1/section4/3_go_and_db.md
index 6125c2d4..d30bd074 100644
--- a/docs/chapter1/section4/3_go_and_db.md
+++ b/docs/chapter1/section4/3_go_and_db.md
@@ -44,7 +44,7 @@ export DB_DATABASE="world"
 
 今回は手元で動いているデータベースを使うのでパスワードなどが知られても問題ありませんが、実際には環境変数など外部の人に知られたくない、GitHub などに上げたくないファイルもあります。そのような場合は、`.gitignore`というファイルを使うことで特定のファイルやフォルダを Git 管理の対象外にできます。`.gitignore`ファイルの最後に`.env`を追記しましょう。
 
-```txt
+```html
 ...
 # Go workspace file
 go.work
@@ -76,7 +76,7 @@ $ go run main.go
 
 出力はこのようになります。
 
-```txt
+```html
 connected
 Tokyoの人口は7980230人です
 ```
@@ -124,7 +124,7 @@ $ go run main.go {都市の名前}
 <<< @/chapter1/section4/src/select.go#main{27 go:line-numbers}
 以下のように日本の都市一覧を取得できます。
 
-```txt
+```html
 connected
 日本の都市一覧
 都市名: Tokyo, 人口: 7980230