fix(mssql): upsert query with falsey values

src/dialects/mssql/query-generator.js

@@ -476,7 +476,7 @@ class MSSQLQueryGenerator extends AbstractQueryGenerator {
        * Exclude NULL Composite PK/UK. Partial Composite clauses should also be excluded as it doesn't guarantee a single row
        */
       for (const key in clause) {
-        if (!clause[key]) {
+        if (typeof clause[key] === 'undefined' || clause[key] == null) {
           valid = false;
           break;
         }

test/unit/dialects/mssql/query-generator.test.js

@@ -3,6 +3,8 @@
 const Support = require('../../support');
 const expectsql = Support.expectsql;
 const current = Support.sequelize;
+const DataTypes = require('../../../../lib/data-types');
+const Op = require('../../../../lib/operators');
 const TableHints = require('../../../../lib/table-hints');
 const QueryGenerator = require('../../../../lib/dialects/mssql/query-generator');
 
@@ -22,6 +24,53 @@ if (current.dialect.name === 'mssql') {
       });
     });
 
+    it('upsertQuery with falsey values', function () {
+      let testTable = this.sequelize.define(
+        'test_table',
+        {
+          Name: {
+            type: DataTypes.STRING,
+            primaryKey: true
+          },
+          Age: {
+            type: DataTypes.INTEGER
+          },
+          IsOnline: {
+            type: DataTypes.BOOLEAN,
+            primaryKey: true
+          }
+        },
+        {
+          freezeTableName: true,
+          timestamps: false
+        }
+      );
+
+      const insertValues = {
+        Name: 'Charlie',
+        Age: 24,
+        IsOnline: false
+      };
+
+      const updateValues = {
+        Age: 24
+      };
+
+      const whereValues = [
+        {
+          Name: 'Charlie',
+          IsOnline: false
+        }
+      ];
+
+      const where = {
+        [Op.or]: whereValues
+      };
+
+      // the main purpose of this test is to validate this does not throw
+      this.queryGenerator.upsertQuery('test_table', updateValues, insertValues, where, testTable);
+    });
+
     it('createDatabaseQuery with collate', function () {
       expectsql(
         this.queryGenerator.createDatabaseQuery('myDatabase', {