Add band and venue follows with concert diary

db/migrations/14_concert_bands.sql

@@ -0,0 +1,7 @@
+CREATE TABLE IF NOT EXISTS concert_bands (
+    concert_id INTEGER NOT NULL REFERENCES concerts(id) ON DELETE CASCADE,
+    band_key VARCHAR(255) NOT NULL,
+    display_name VARCHAR(255) NOT NULL,
+    position SMALLINT NOT NULL DEFAULT 0,
+    PRIMARY KEY (concert_id, band_key)
+);