diff --git a/debug/checksum-db.js b/debug/checksum-db.js
index e893653..ce182ee 100644
--- a/debug/checksum-db.js
+++ b/debug/checksum-db.js
@@ -26,9 +26,9 @@ function listTables() {
 
 function checksumTable(table) {
     return new Promise((resolve, reject) => {
-        DB.query("CHECKSUM TABLE " + table).then(result => {
+        DB.query("CHECKSUM TABLE ??", [table]).then(result => {
             let checksum = result[0].Checksum;
-            DB.query("SELECT COUNT(*) AS rec_count FROM " + table)
+            DB.query("SELECT COUNT(*) AS rec_count FROM ??", [table])
                 .then(result => resolve({ table, rec_count: result[0].rec_count, checksum }))
                 .catch(error => reject(error))
         }).catch(error => reject(error))
diff --git a/src/backup/slave.js b/src/backup/slave.js
index fd860d2..315e101 100644
--- a/src/backup/slave.js
+++ b/src/backup/slave.js
@@ -316,7 +316,7 @@ function deleteTableData(data) {
         data.forEach(r => r.t_name in delete_needed ? delete_needed[r.t_name].push(r.id) : delete_needed[r.t_name] = [r.id]);
         let queries = [];
         for (let table in delete_needed)
-            queries.push("DELETE FROM ?? WHERE id IN (?)", [table, delete_needed[table]]);
+            queries.push(["DELETE FROM ?? WHERE id IN (?)", [table, delete_needed[table]]]);
         DB.transaction(queries).then(_ => resolve(true)).catch(error => reject(error));
     })
 }
diff --git a/src/backup/sync.js b/src/backup/sync.js
index 087233f..313e2d8 100644
--- a/src/backup/sync.js
+++ b/src/backup/sync.js
@@ -139,7 +139,7 @@ function getTableHashes(table) {
             //columns
             let columns = result.map(r => r["Field"]).sort();
             //select statement
-            let statement = "SELECT CEIL(id/?) as group_id";
+            let statement = "SELECT CEIL(id/?) as group_id,";
             let query_values = [HASH_N_ROW];
             //aggregate column values
             let col_aggregate = columns.map(c => "IFNULL(CRC32(??), 0)").join('+');