feat(binary-operators): Added date minus date (#388)

src/schema/pg-catalog/binary-operators.ts

@@ -68,6 +68,16 @@ function registerNumericOperators(schema: _ISchema) {
 
 
 function registerDatetimeOperators(schema: _ISchema) {
+    // ======= date "-" date =======
+    schema.registerOperator({
+        operator: '-',
+        commutative: false,
+        left: Types.date,
+        right: Types.date,
+        returns: Types.interval,
+        implementation: (a, b) => moment(a).diff(moment(b), 'days'),
+    })
+
     // ======= date/time "+ -" timestamp =======
     for (const dt of dateTypes) {
         for (const [operator, f] of [['+', 1], ['-', -1]] as const) {

src/tests/operators.queries.spec.ts

@@ -56,6 +56,23 @@ describe('Operators', () => {
         expect(dt.toString()).to.equal(moment.utc().startOf('day').add(1, 'day').toDate().toString());
     });
 
+    it('date - date', () => {
+        const result = many(`select '2020-01-02'::date - '2020-01-01'::date as dt`);
+        expect(result[0]?.dt).to.equal(1);
+        const result2 = many(`select '2020-01-03'::date - '2020-01-01'::date as dt`);
+        expect(result2[0]?.dt).to.equal(2);
+        const result3 = many(`select '2022-01-01'::date - '2020-01-01'::date as dt`);
+        expect(result3[0]?.dt).to.equal(731);
+
+        const nullResult1 = many(`select '2020-01-03'::date - null::date as dt`);
+        expect(nullResult1[0]?.dt).to.equal(null);
+
+        const nullResult2 = many(`select null::date - '2020-01-03'::date as dt`);
+        expect(nullResult2[0]?.dt).to.equal(null);
+
+        const nullResult3 = many(`select null::date - null::date as dt`);
+        expect(nullResult3[0]?.dt).to.equal(null);
+    });
 
     it('timestamp + interval', () => {
         const result = many(`select now() + interval '1 day' as dt`);