diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/command/ShowTablesSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/command/ShowTablesSuite.scala
index 2cc4a42ee1e95..f03af47c4dbf2 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/command/ShowTablesSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/command/ShowTablesSuite.scala
@@ -18,11 +18,14 @@
 package org.apache.spark.sql.execution.command
 
 import org.apache.spark.sql.{QueryTest, Row}
+import org.apache.spark.sql.connector.catalog.CatalogV2Implicits._
+import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.test.SharedSparkSession
 import org.apache.spark.sql.types.StructType
 
 trait ShowTablesSuite extends QueryTest with SharedSparkSession {
   protected def catalog: String
+  protected def defaultNamespace: Seq[String]
   protected def defaultUsing: String
   case class ShowRow(namespace: String, table: String, isTemporary: Boolean)
   protected def getRows(showRows: Seq[ShowRow]): Seq[Row]
@@ -36,47 +39,74 @@ trait ShowTablesSuite extends QueryTest with SharedSparkSession {
   }
 
   test("show an existing table") {
-    val namespace = "test"
-    val table = "people"
-    withDatabase(s"$catalog.$namespace") {
-      sql(s"CREATE DATABASE $catalog.$namespace")
-      withTable(s"$catalog.$namespace.$table") {
-        sql(s"CREATE TABLE $catalog.$namespace.$table (name STRING, id INT) $defaultUsing")
-        runShowTablesSql(s"SHOW TABLES IN $catalog.test", Seq(ShowRow(namespace, table, false)))
+    withNamespace(s"$catalog.ns") {
+      sql(s"CREATE NAMESPACE $catalog.ns")
+      withTable(s"$catalog.ns.table") {
+        sql(s"CREATE TABLE $catalog.ns.table (name STRING, id INT) $defaultUsing")
+        runShowTablesSql(s"SHOW TABLES IN $catalog.ns", Seq(ShowRow("ns", "table", false)))
       }
     }
   }
 
   test("show tables with a pattern") {
-    withDatabase(s"$catalog.db", s"$catalog.db2") {
-      sql(s"CREATE DATABASE $catalog.db")
-      sql(s"CREATE DATABASE $catalog.db2")
+    withNamespace(s"$catalog.ns1", s"$catalog.ns2") {
+      sql(s"CREATE NAMESPACE $catalog.ns1")
+      sql(s"CREATE NAMESPACE $catalog.ns2")
       withTable(
-        s"$catalog.db.table",
-        s"$catalog.db.table_name_1",
-        s"$catalog.db.table_name_2",
-        s"$catalog.db2.table_name_2") {
-        sql(s"CREATE TABLE $catalog.db.table (id bigint, data string) $defaultUsing")
-        sql(s"CREATE TABLE $catalog.db.table_name_1 (id bigint, data string) $defaultUsing")
-        sql(s"CREATE TABLE $catalog.db.table_name_2 (id bigint, data string) $defaultUsing")
-        sql(s"CREATE TABLE $catalog.db2.table_name_2 (id bigint, data string) $defaultUsing")
+        s"$catalog.ns1.table",
+        s"$catalog.ns1.table_name_1",
+        s"$catalog.ns1.table_name_2",
+        s"$catalog.ns2.table_name_2") {
+        sql(s"CREATE TABLE $catalog.ns1.table (id bigint, data string) $defaultUsing")
+        sql(s"CREATE TABLE $catalog.ns1.table_name_1 (id bigint, data string) $defaultUsing")
+        sql(s"CREATE TABLE $catalog.ns1.table_name_2 (id bigint, data string) $defaultUsing")
+        sql(s"CREATE TABLE $catalog.ns2.table_name_2 (id bigint, data string) $defaultUsing")
 
         runShowTablesSql(
-          s"SHOW TABLES FROM $catalog.db",
+          s"SHOW TABLES FROM $catalog.ns1",
           Seq(
-            ShowRow("db", "table", false),
-            ShowRow("db", "table_name_1", false),
-            ShowRow("db", "table_name_2", false)))
+            ShowRow("ns1", "table", false),
+            ShowRow("ns1", "table_name_1", false),
+            ShowRow("ns1", "table_name_2", false)))
 
         runShowTablesSql(
-          s"SHOW TABLES FROM $catalog.db LIKE '*name*'",
+          s"SHOW TABLES FROM $catalog.ns1 LIKE '*name*'",
           Seq(
-            ShowRow("db", "table_name_1", false),
-            ShowRow("db", "table_name_2", false)))
+            ShowRow("ns1", "table_name_1", false),
+            ShowRow("ns1", "table_name_2", false)))
 
         runShowTablesSql(
-          s"SHOW TABLES FROM $catalog.db LIKE '*2'",
-          Seq(ShowRow("db", "table_name_2", false)))
+          s"SHOW TABLES FROM $catalog.ns1 LIKE '*2'",
+          Seq(ShowRow("ns1", "table_name_2", false)))
+      }
+    }
+  }
+
+  test("show tables with current catalog and namespace") {
+    withSQLConf(SQLConf.DEFAULT_CATALOG.key -> catalog) {
+      val tblName = (catalog +: defaultNamespace :+ "table").quoted
+      withTable(tblName) {
+        sql(s"CREATE TABLE $tblName (name STRING, id INT) $defaultUsing")
+        val ns = defaultNamespace.mkString(".")
+        runShowTablesSql("SHOW TABLES", Seq(ShowRow(ns, "table", false)))
+      }
+    }
+  }
+
+  test("change current catalog and namespace with USE statements") {
+    withNamespace(s"$catalog.ns") {
+      sql(s"CREATE NAMESPACE $catalog.ns")
+      withTable(s"$catalog.ns.table") {
+        sql(s"CREATE TABLE $catalog.ns.table (name STRING, id INT) $defaultUsing")
+
+        sql(s"USE $catalog")
+        // No table is matched since the current namespace is not ["ns"]
+        assert(defaultNamespace != Seq("ns"))
+        runShowTablesSql("SHOW TABLES", Seq())
+
+        // Update the current namespace to match "ns.tbl".
+        sql(s"USE $catalog.ns")
+        runShowTablesSql("SHOW TABLES", Seq(ShowRow("ns", "table", false)))
       }
     }
   }
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/command/v1/ShowTablesSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/command/v1/ShowTablesSuite.scala
index 5537ad372ac25..49303b8914e83 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/command/v1/ShowTablesSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/command/v1/ShowTablesSuite.scala
@@ -21,11 +21,11 @@ import org.apache.spark.sql.{AnalysisException, Row}
 import org.apache.spark.sql.catalyst.analysis.NoSuchDatabaseException
 import org.apache.spark.sql.connector.catalog.CatalogManager
 import org.apache.spark.sql.execution.command.{ShowTablesSuite => CommonShowTablesSuite}
-import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.types.{BooleanType, StringType, StructType}
 
 class ShowTablesSuite extends CommonShowTablesSuite {
   override def catalog: String = CatalogManager.SESSION_CATALOG_NAME
+  override def defaultNamespace: Seq[String] = Seq("default")
   override protected def defaultUsing: String = "USING parquet"
   override protected def showSchema: StructType = {
     new StructType()
@@ -57,15 +57,6 @@ class ShowTablesSuite extends CommonShowTablesSuite {
     assert(msg.contains("Database 'unknown' not found"))
   }
 
-  test("namespace is not specified and the default catalog is set") {
-    withSQLConf(SQLConf.DEFAULT_CATALOG.key -> catalog) {
-      withTable("table") {
-        spark.sql(s"CREATE TABLE table (id bigint, data string) $defaultUsing")
-        runShowTablesSql("SHOW TABLES", Seq(ShowRow("default", "table", false)))
-      }
-    }
-  }
-
   // `SHOW TABLES` from v2 catalog returns empty result.
   test("v1 SHOW TABLES list the temp views") {
     withSourceViews {
@@ -75,23 +66,14 @@ class ShowTablesSuite extends CommonShowTablesSuite {
     }
   }
 
-  test("using v1 catalog, db name with multipartIdentifier ('a.b') is not allowed.") {
+  test("v1 SHOW TABLES only support single-level namespace") {
     val exception = intercept[AnalysisException] {
       runShowTablesSql("SHOW TABLES FROM a.b", Seq())
     }
     assert(exception.getMessage.contains("The database name is not valid: a.b"))
   }
 
-  test("namespace not specified and default v2 catalog not set - fallback to v1") {
-    withSourceViews {
-      runShowTablesSql(
-        "SHOW TABLES",
-        Seq(ShowRow("", "source", true), ShowRow("", "source2", true)))
-      runShowTablesSql("SHOW TABLES LIKE '*2'", Seq(ShowRow("", "source2", true)))
-    }
-  }
-
-  test("SHOW TABLE EXTENDED for default") {
+  test("SHOW TABLE EXTENDED from default") {
     withSourceViews {
       val expected = Seq(Row("", "source", true), Row("", "source2", true))
       val schema = new StructType()
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/command/v2/ShowTablesSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/command/v2/ShowTablesSuite.scala
index aabc20b1370f4..1de09805ec6a5 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/command/v2/ShowTablesSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/command/v2/ShowTablesSuite.scala
@@ -22,12 +22,12 @@ import org.apache.spark.sql.{AnalysisException, QueryTest, Row}
 import org.apache.spark.sql.catalyst.analysis.NoSuchDatabaseException
 import org.apache.spark.sql.connector.InMemoryTableCatalog
 import org.apache.spark.sql.execution.command.{ShowTablesSuite => CommonShowTablesSuite}
-import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.test.SharedSparkSession
 import org.apache.spark.sql.types.{StringType, StructType}
 
 class ShowTablesSuite extends QueryTest with SharedSparkSession with CommonShowTablesSuite {
   override def catalog: String = "test_catalog_v2"
+  override def defaultNamespace: Seq[String] = Nil
   override protected def defaultUsing: String = "USING _"
   override protected def showSchema: StructType = {
     new StructType()
@@ -71,16 +71,6 @@ class ShowTablesSuite extends QueryTest with SharedSparkSession with CommonShowT
     }
   }
 
-  test("namespace is not specified and the default catalog is set") {
-    withSQLConf(SQLConf.DEFAULT_CATALOG.key -> catalog) {
-      withTable("table") {
-        spark.sql(s"CREATE TABLE table (id bigint, data string) $defaultUsing")
-        // TODO(SPARK-33403): DSv2 SHOW TABLES doesn't show `default`
-        runShowTablesSql("SHOW TABLES", Seq(ShowRow("", "table", false)))
-      }
-    }
-  }
-
   // The test fails for V1 catalog with the error:
   // org.apache.spark.sql.AnalysisException:
   //   The namespace in session catalog must have exactly one name part: spark_catalog.ns1.ns2.tbl
@@ -111,23 +101,6 @@ class ShowTablesSuite extends QueryTest with SharedSparkSession with CommonShowT
     }
   }
 
-  // The test fails with the error in V1 session catalog:
-  // org.apache.spark.sql.AnalysisException:
-  // The namespace in session catalog must have exactly one name part: spark_catalog.ns1.ns2.table
-  test("change current catalog and namespace with USE statements") {
-    withTable(s"$catalog.ns1.ns2.table") {
-      sql(s"CREATE TABLE $catalog.ns1.ns2.table (id bigint) $defaultUsing")
-
-      // Update the current catalog, and no table is matched since the current namespace is Array().
-      sql(s"USE $catalog")
-      runShowTablesSql("SHOW TABLES", Seq())
-
-      // Update the current namespace to match ns1.ns2.table.
-      sql(s"USE $catalog.ns1.ns2")
-      runShowTablesSql("SHOW TABLES", Seq(ShowRow("ns1.ns2", "table", false)))
-    }
-  }
-
   // TODO(SPARK-33393): Support SHOW TABLE EXTENDED in DSv2
   test("SHOW TABLE EXTENDED: an existing table") {
     val table = "people"