Fix for bug#45998: database crashes when running

"create as select" (innodb table)

Problem: code constructing "CREATE TABLE..." statement
doesn't take into account that current database is not set
in some cases. That may lead to a server crash.

Fix: check if current database is set.

mysql-test/extra/binlog_tests/binlog.test

@@ -258,3 +258,15 @@ dec $it;
 }
 show master status /* must show new binlog index after rotating */;
 drop table t3;
+
+--echo #
+--echo # Bug #45998: database crashes when running "create as select"
+--echo #
+CREATE DATABASE test1;
+USE test1;
+DROP DATABASE test1;
+CREATE TABLE test.t1(a int);
+INSERT INTO test.t1 VALUES (1), (2);
+CREATE TABLE test.t2 SELECT * FROM test.t1;
+USE test;
+DROP TABLES t1, t2;

mysql-test/suite/binlog/r/binlog_row_binlog.result

@@ -1298,3 +1298,14 @@ show master status /* must show new binlog index after rotating */;
 File	Position	Binlog_Do_DB	Binlog_Ignore_DB
 master-bin.000002	106		
 drop table t3;
+#
+# Bug #45998: database crashes when running "create as select"
+#
+CREATE DATABASE test1;
+USE test1;
+DROP DATABASE test1;
+CREATE TABLE test.t1(a int);
+INSERT INTO test.t1 VALUES (1), (2);
+CREATE TABLE test.t2 SELECT * FROM test.t1;
+USE test;
+DROP TABLES t1, t2;

sql/sql_show.cc

@@ -1151,7 +1151,7 @@ int store_create_info(THD *thd, TABLE_LIST *table_list, String *packet,
   {
     const LEX_STRING *const db=
       table_list->schema_table ? &INFORMATION_SCHEMA_NAME : &table->s->db;
-    if (strcmp(db->str, thd->db) != 0)
+    if (!thd->db || strcmp(db->str, thd->db))
     {
       append_identifier(thd, packet, db->str, db->length);
       packet->append(STRING_WITH_LEN("."));