diff --git a/src/common/error/src/status_code.rs b/src/common/error/src/status_code.rs
index 2afcbc278d..2b0a338b31 100644
--- a/src/common/error/src/status_code.rs
+++ b/src/common/error/src/status_code.rs
@@ -1,17 +1,22 @@
 /// Common status code for public API.
 #[derive(Debug, Clone, Copy)]
 pub enum StatusCode {
-    // ====== Begin of common status code ===========
+    // ====== Begin of common status code ==============
     /// Unknown error.
     Unknown,
     /// Unsupported operation.
     Unsupported,
     /// Internal server error.
     Internal,
-    // ====== End of common status code =============
+    // ====== End of common status code ================
 
-    // ====== Begin of SQL related status code ======
+    // ====== Begin of SQL related status code =========
     /// SQL Syntax error.
     InvalidSyntax,
-    // ====== End of SQL related status code ========
+    // ====== End of SQL related status code ===========
+
+    // ====== Begin of catalog related status code =====
+    /// Table already exists.
+    TableAlreadyExists,
+    // ====== End of catalog related status code =======
 }
diff --git a/src/datanode/src/error.rs b/src/datanode/src/error.rs
index 6b4762d008..de767ffe8c 100644
--- a/src/datanode/src/error.rs
+++ b/src/datanode/src/error.rs
@@ -1,5 +1,4 @@
 use common_error::prelude::*;
-use snafu::Snafu;
 
 /// Business error of datanode.
 #[derive(Debug, Snafu)]
diff --git a/src/query/src/catalog/memory.rs b/src/query/src/catalog/memory.rs
index 6c4aa8be41..e2c194c001 100644
--- a/src/query/src/catalog/memory.rs
+++ b/src/query/src/catalog/memory.rs
@@ -3,6 +3,7 @@ use std::collections::HashMap;
 use std::sync::Arc;
 use std::sync::RwLock;
 
+use common_error::prelude::*;
 use table::table::numbers::NumbersTable;
 use table::TableRef;
 
@@ -11,8 +12,32 @@ use crate::catalog::{
     CatalogList, CatalogListRef, CatalogProvider, CatalogProviderRef, DEFAULT_CATALOG_NAME,
     DEFAULT_SCHEMA_NAME,
 };
-use crate::error::Result;
-use crate::query_engine::datafusion::error;
+use crate::error::{Error, Result};
+
+/// Error implementation of memory catalog.
+#[derive(Debug, Snafu)]
+pub enum InnerError {
+    #[snafu(display("Table {} already exists", table))]
+    TableExists { table: String, backtrace: Backtrace },
+}
+
+impl ErrorExt for InnerError {
+    fn status_code(&self) -> StatusCode {
+        match self {
+            InnerError::TableExists { .. } => StatusCode::TableAlreadyExists,
+        }
+    }
+
+    fn backtrace_opt(&self) -> Option<&Backtrace> {
+        ErrorCompat::backtrace(self)
+    }
+}
+
+impl From<InnerError> for Error {
+    fn from(err: InnerError) -> Self {
+        Self::new(err)
+    }
+}
 
 /// Simple in-memory list of catalogs
 #[derive(Default)]
@@ -129,10 +154,7 @@ impl SchemaProvider for MemorySchemaProvider {
     fn register_table(&self, name: String, table: TableRef) -> Result<Option<TableRef>> {
         if self.table_exist(name.as_str()) {
             // FIXME(yingwen): Define another error.
-            return error::ExecutionSnafu {
-                message: format!("The table {} already exists", name),
-            }
-            .fail()?;
+            return TableExistsSnafu { table: name }.fail()?;
         }
         let mut tables = self.tables.write().unwrap();
         Ok(tables.insert(name, table))
diff --git a/src/query/src/query_engine/datafusion/error.rs b/src/query/src/query_engine/datafusion/error.rs
index 5798b20e9f..1d89deacd2 100644
--- a/src/query/src/query_engine/datafusion/error.rs
+++ b/src/query/src/query_engine/datafusion/error.rs
@@ -1,6 +1,5 @@
 use common_error::prelude::*;
 use datafusion::error::DataFusionError;
-use snafu::{Backtrace, ErrorCompat, Snafu};
 
 use crate::error::Error;
 
@@ -28,14 +27,21 @@ pub enum InnerError {
         source: DataFusionError,
         backtrace: Backtrace,
     },
-
-    #[snafu(display("Execution error: {}", message))]
-    Execution { message: String },
 }
 
-// TODO(yingwen): Implement status_code().
 impl ErrorExt for InnerError {
-    fn backtrace_opt(&self) -> Option<&snafu::Backtrace> {
+    fn status_code(&self) -> StatusCode {
+        use InnerError::*;
+
+        match self {
+            ParseSql { source, .. } => source.status_code(),
+            Datafusion { .. } | PhysicalPlanDowncast { .. } | Planner { .. } => {
+                StatusCode::Internal
+            }
+        }
+    }
+
+    fn backtrace_opt(&self) -> Option<&Backtrace> {
         ErrorCompat::backtrace(self)
     }
 }