From 237590f9eb8fe894d29a142a531f4475d76f178f Mon Sep 17 00:00:00 2001
From: wshwsh12 <793703860@qq.com>
Date: Fri, 3 Apr 2020 23:47:43 +0800
Subject: [PATCH 1/2] add union stmt flag

---
 executor/executor.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/executor/executor.go b/executor/executor.go
index a2853f3cec2e2..f804d23362029 100644
--- a/executor/executor.go
+++ b/executor/executor.go
@@ -1610,6 +1610,11 @@ func ResetContextOfStmt(ctx sessionctx.Context, s ast.StmtNode) (err error) {
 			sc.Priority = opts.Priority
 			sc.NotFillCache = !opts.SQLCache
 		}
+	case *ast.UnionStmt:
+		sc.OverflowAsWarning = true
+		sc.IgnoreTruncate = true
+		sc.IgnoreZeroInDate = true
+		sc.AllowInvalidDate = vars.SQLMode.HasAllowInvalidDatesMode()
 	case *ast.ShowStmt:
 		sc.IgnoreTruncate = true
 		sc.IgnoreZeroInDate = true

From 0198c3c1aaa4a1ecd2d44d88c847d6d02b52918f Mon Sep 17 00:00:00 2001
From: wshwsh12 <793703860@qq.com>
Date: Sat, 4 Apr 2020 00:01:00 +0800
Subject: [PATCH 2/2] add some test

---
 executor/executor.go           |  3 ++-
 expression/integration_test.go | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/executor/executor.go b/executor/executor.go
index f804d23362029..baee88e78d760 100644
--- a/executor/executor.go
+++ b/executor/executor.go
@@ -1611,8 +1611,9 @@ func ResetContextOfStmt(ctx sessionctx.Context, s ast.StmtNode) (err error) {
 			sc.NotFillCache = !opts.SQLCache
 		}
 	case *ast.UnionStmt:
+		sc.InSelectStmt = true
 		sc.OverflowAsWarning = true
-		sc.IgnoreTruncate = true
+		sc.TruncateAsWarning = true
 		sc.IgnoreZeroInDate = true
 		sc.AllowInvalidDate = vars.SQLMode.HasAllowInvalidDatesMode()
 	case *ast.ShowStmt:
diff --git a/expression/integration_test.go b/expression/integration_test.go
index ba065b81c1d65..5470ab9839889 100755
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -5971,3 +5971,13 @@ func (s *testIntegrationSuite) TestNegativeZeroForHashJoin(c *C) {
 	tk.MustExec("drop TABLE t0;")
 	tk.MustExec("drop table t1;")
 }
+
+func (s *testIntegrationSuite) TestIssue15790(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test;")
+	tk.MustExec("CREATE TABLE t0(c0 INT);")
+	tk.MustExec("INSERT INTO t0(c0) VALUES (0);")
+	tk.MustQuery("SELECT * FROM t0 WHERE -10000000000000000000 | t0.c0 UNION SELECT * FROM t0;").Check(testkit.Rows("0"))
+	tk.MustQuery("SELECT * FROM t0 WHERE -10000000000000000000 | t0.c0 UNION all SELECT * FROM t0;").Check(testkit.Rows("0", "0"))
+	tk.MustExec("drop table t0;")
+}