Applying tdd on select-only exercise

exercises/concept/intro-select/create_fixture.sql

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+DROP TABLE IF EXISTS weather_readings;
+CREATE TABLE weather_readings (
+  date        TEXT    NOT NULL,
+  location    TEXT    NOT NULL,
+  temperature REAL    NOT NULL,
+  humidity    INTEGER NOT NULL
+);
+
+.mode csv
+.import ./data.csv weather_readings

exercises/concept/intro-select/data.csv

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+"2025-10-22","Portland",53.1,72
+"2025-10-22","Seattle",56.2,66
+"2025-10-22","Boise",60.4,55
+"2025-10-23","Portland",54.6,70
+"2025-10-23","Seattle",57.8,68
+"2025-10-23","Boise",62.0,58

exercises/concept/intro-select/intro-select.sql

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+.print
+.print "All data"
+.print "========"
+.print
+SELECT * FROM weather_readings;
+
+.print 
+.print "Location and temperature only"
+.print "============================="
+.print
+SELECT location, temperature FROM weather_readings;
+
+.print 
+.print "Greeting"
+.print "========"
+.print
+-- This one will fail on purpose
+SELECT 'Hello, world.' AS say_hi;
+
+.print 
+.print "Data for Seattle"
+.print "================"
+.print
+SELECT * FROM weather_readings WHERE location = 'Seattle';
+
+.print 
+.print "Data with humidity constraints"
+.print "=============================="
+.print
+SELECT * FROM weather_readings WHERE humidity BETWEEN 60 AND 70;
+
+.print 
+.print "Locations"
+.print "========="
+.print
+SELECT location FROM weather_readings;
+
+.print 
+.print "Unique locations"
+.print "================"
+.print
+SELECT DISTINCT location FROM weather_readings;

exercises/concept/intro-select/intro-select_exemplar.sql

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+.print
+.print "All data"
+.print "========"
+.print
+SELECT * FROM weather_readings;
+
+.print 
+.print "Location and temperature only"
+.print "============================="
+.print
+SELECT location, temperature FROM weather_readings;
+
+.print 
+.print "Greeting"
+.print "========"
+.print
+SELECT 'Hello, world.';
+
+.print 
+.print "Data for Seattle"
+.print "================"
+.print
+SELECT * FROM weather_readings WHERE location = 'Seattle';
+
+.print 
+.print "Data with humidity constraints"
+.print "=============================="
+.print
+SELECT * FROM weather_readings WHERE humidity BETWEEN 60 AND 70;
+
+.print 
+.print "Locations"
+.print "========="
+.print
+SELECT location FROM weather_readings;
+
+.print 
+.print "Unique locations"
+.print "================"
+.print
+SELECT DISTINCT location FROM weather_readings;

exercises/concept/intro-select/intro-select_test.sql

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+-- Create database:
+.read ./create_fixture.sql
+
+.mode columns
+
+-- Generate expected output
+.output expected_output.txt
+.read ./intro-select_exemplar.sql
+
+-- Run user solution
+.output user_output.txt
+.read ./intro-select.sql
+
+-- Compare expected vs actual
+.shell diff expected_output.txt user_output.txt
+