diff --git a/db_deploy.sql b/db_deploy.sql
index 9388bbf..37cb718 100644
--- a/db_deploy.sql
+++ b/db_deploy.sql
@@ -68,19 +68,21 @@ COMMENT ON COLUMN evt.gl.bprkeys IS 'extract from initial basic pecuniary record
 
 CREATE TABLE evt.bal (
     acct ltree REFERENCES evt.acct(acct)
-    ,perd ltree REFERENCES evt.fspr(id)
+    ,fspr ltree REFERENCES evt.fspr(id)
     ,obal numeric(12,2)
     ,debits numeric(12,2)
     ,credits numeric(12,2)
     ,cbal numeric(12,2)
 );
+ALTER TABLE evt.bal ADD CONSTRAINT bal_pk PRIMARY KEY(acct,fspr);
 COMMENT ON COLUMN evt.bal.acct IS 'account';
-COMMENT ON COLUMN evt.bal.perd IS 'period';
+COMMENT ON COLUMN evt.bal.fspr IS 'period';
 COMMENT ON COLUMN evt.bal.obal IS 'opening balance';
 COMMENT ON COLUMN evt.bal.debits IS 'total debits';
 COMMENT ON COLUMN evt.bal.credits IS 'total credits';
 COMMENT ON COLUMN evt.bal.cbal IS 'closing balance';
 
+
 ---------------------------handle new logged event----------------------------------------
 
 CREATE OR REPLACE FUNCTION evt.log_insert() RETURNS trigger
diff --git a/schema/tables/bal.sql b/schema/tables/bal.sql
index 1f697d7..e50e65e 100644
--- a/schema/tables/bal.sql
+++ b/schema/tables/bal.sql
@@ -2,15 +2,16 @@
 
 CREATE TABLE evt.bal (
     acct ltree REFERENCES evt.acct(acct)
-    ,perd ltree REFERENCES evt.fspr(id)
+    ,fspr ltree REFERENCES evt.fspr(id)
     ,obal numeric(12,2)
     ,debits numeric(12,2)
     ,credits numeric(12,2)
     ,cbal numeric(12,2)
 );
+ALTER TABLE evt.bal ADD CONSTRAINT bal_pk PRIMARY KEY(acct,fspr);
 COMMENT ON COLUMN evt.bal.acct IS 'account';
-COMMENT ON COLUMN evt.bal.perd IS 'period';
+COMMENT ON COLUMN evt.bal.fspr IS 'period';
 COMMENT ON COLUMN evt.bal.obal IS 'opening balance';
 COMMENT ON COLUMN evt.bal.debits IS 'total debits';
 COMMENT ON COLUMN evt.bal.credits IS 'total credits';
-COMMENT ON COLUMN evt.bal.cbal IS 'closing balance';
\ No newline at end of file
+COMMENT ON COLUMN evt.bal.cbal IS 'closing balance';