ADDED   data/sql/schema.sql
Index: data/sql/schema.sql
==================================================================
--- /dev/null
+++ data/sql/schema.sql
@@ -0,0 +1,96 @@
+BEGIN;
+PRAGMA foreign_keys = ON;
+
+CREATE TABLE spatial (
+    id INTEGER PRIMARY KEY,
+    latitude REAL,
+    longitude REAL,
+    off_name TEXT NOT NULL,
+    lang TEXT NOT NULL CHECK (lang IN ('RUS', 'CHU', 'HIM', 'MEM', 'ERZ', 'TAT', 'UNK')),
+    toponym_class TEXT NOT NULL,
+    toponym_type TEXT NOT NULL,
+    district TEXT,
+    doubt INTEGER NULL CHECK (doubt IN ('', 1)),
+    landmark TEXT,
+    comments TEXT,
+    other TEXT,
+    CHECK ((latitude = '' AND longitude = '')
+        OR (latitude != '' AND longitude != '' AND
+            latitude BETWEEN 54.62 AND 56.4 AND
+            longitude BETWEEN 45.87 AND 48.48))
+);
+
+CREATE TABLE water (
+    id INTEGER PRIMARY KEY,
+    spatial_id INTEGER,
+    spatial_off_name TEXT,
+    water_type TEXT NOT NULL,
+    water_wkt TEXT UNIQUE NOT NULL,
+    FOREIGN KEY (spatial_id, spatial_off_name)
+        REFERENCES spatial (id, off_name)
+        ON UPDATE CASCADE
+        ON DELETE CASCADE
+);
+
+CREATE TABLE linguistic (
+    id INTEGER PRIMARY KEY,
+    spatial_id INTEGER,
+    doubt_spatial INTEGER CHECK (doubt_spatial IN ('', 1)),
+    main_id INTEGER,
+    toponym TEXT NOT NULL,
+    toponym_forms TEXT NOT NULL,
+    doubt_toponym INTEGER CHECK (doubt_toponym IN ('', 1)),
+    lang TEXT NOT NULL,
+    doubt_lang INTEGER CHECK (doubt_lang IN ('', 1)),
+    pronunciation TEXT,
+    doubt_pronunciation INTEGER CHECK (doubt_pronunciation IN ('', 1)),
+    etym TEXT,
+    origin TEXT,
+    comments TEXT,
+    other TEXT,
+    FOREIGN KEY (spatial_id)
+        REFERENCES spatial (spatial_id)
+        ON UPDATE CASCADE
+        ON DELETE CASCADE,
+    FOREIGN KEY (main_id)
+        REFERENCES linguistic (id)
+        ON UPDATE CASCADE
+        ON DELETE CASCADE
+);
+
+CREATE TABLE sources (
+    id INTEGER PRIMARY KEY,
+    source_type TEXT NOT NULL,
+    title TEXT NOT NULL,
+    source_year INTEGER NOT NULL CHECK (source_year > 100 AND source_year < 2026),
+    citation TEXT UNIQUE NOT NULL,
+    url TEXT UNIQUE,
+    digital_copy TEXT CHECK (digital_copy IN ('yes', 'no')),
+    comments TEXT,
+    other TEXT
+);
+
+CREATE TABLE temporal (
+    id INTEGER PRIMARY KEY,
+    linguistic_id INTEGER,
+    linguistic_name TEXT,
+    nest_id INTEGER NOT NULL,
+    start_year INTEGER NOT NULL CHECK (start_year > 100 AND start_year < 2025),
+    doubt_start INTEGER CHECK (doubt_start IN ('', 1)),
+    end_year TEXT CHECK ((end_year = '') OR (CAST(end_year AS INTEGER) BETWEEN 100 AND 2025)),
+    doubt_end INTEGER CHECK (doubt_end IN ('', 1)),
+    comments TEXT,
+    other TEXT,
+    fulltext TEXT,
+    FOREIGN KEY (linguistic_id, linguistic_name)
+        REFERENCES linguistic (id, toponym)
+        ON UPDATE CASCADE
+        ON DELETE CASCADE,
+    FOREIGN KEY (nest_id)
+        REFERENCES temporal (id)
+        ON UPDATE CASCADE
+        ON DELETE CASCADE
+);
+
+COMMIT;
+