[ADD] Solution to task related to data separation

Author: stivenramireza

tasks/05-data-separation.sql

@@ -0,0 +1,83 @@
+-- Tarea con countryLanguage
+SELECT *
+FROM countrylanguage;
+
+-- Crear la tabla de language
+SELECT *
+FROM language;
+
+-- Sequence and defined type
+CREATE SEQUENCE IF NOT EXISTS language_code_seq;
+
+ALTER SEQUENCE language_code_seq RESTART WITH 1;
+
+-- Table Definition
+CREATE TABLE "public"."language" (
+    "code" int4 NOT NULL DEFAULT 	nextval('language_code_seq'::regclass),
+    "name" text NOT NULL,
+    PRIMARY KEY ("code")
+);
+
+-- Crear una columna en countrylanguage
+ALTER TABLE countrylanguage
+ADD COLUMN languagecode varchar(3);
+
+-- Insertar los idiomas en la tabla language
+SELECT DISTINCT(language)
+FROM countrylanguage
+ORDER BY language ASC;
+
+INSERT INTO language (name)
+SELECT DISTINCT(language)
+FROM countrylanguage
+ORDER BY language ASC;
+
+-- Empezar con el select para confirmar lo que vamos a actualizar
+SELECT
+	cl.language,
+	cl.languagecode,
+	(
+		SELECT l.name
+		FROM language AS l
+		WHERE l.name = cl.language
+	)
+FROM countrylanguage AS cl;
+
+-- Actualizar todos los registros
+UPDATE countrylanguage AS cl
+SET languagecode = (
+	SELECT l.code
+	FROM language AS l
+	WHERE l.name = cl.language
+);
+
+-- Cambiar tipo de dato en countrylanguage - languagecode por int4
+ALTER TABLE countrylanguage
+ALTER COLUMN languagecode TYPE INT4
+USING languagecode::INTEGER;
+
+-- Crear el foreign key y constraints de no nulo el language_code
+ALTER TABLE countrylanguage
+ALTER COLUMN languagecode SET NOT NULL;
+
+ALTER TABLE countrylanguage
+ADD CONSTRAINT fk_language_code
+FOREIGN KEY (languagecode)
+REFERENCES language (code);
+
+-- Revisar lo creado
+SELECT *
+FROM countrylanguage;
+
+SELECT *
+FROM language;
+
+SELECT
+	cl.language,
+	cl.languagecode,
+	(
+		SELECT l.name
+		FROM language AS l
+		WHERE l.code = cl.languagecode
+	)
+FROM countrylanguage AS cl;