diff --git a/columnq/src/table/mod.rs b/columnq/src/table/mod.rs
index db6d5a5..95fec0c 100644
--- a/columnq/src/table/mod.rs
+++ b/columnq/src/table/mod.rs
@@ -412,23 +412,29 @@ impl TableSource {
         Ok(match (&self.option, &self.io_source) {
             (Some(opt), _) => opt.extension(),
             (None, TableIoSource::Uri(uri)) => {
-                let ext = Path::new(uri)
-                    .extension()
-                    .and_then(OsStr::to_str)
-                    .ok_or_else(|| {
-                        ColumnQError::InvalidUri(format!(
-                            "cannot detect table extension from uri: {}",
-                            uri
-                        ))
-                    })?;
-
-                match ext {
-                    "csv" | "json" | "parquet" | "ndjson" | "arrow" | "arrows" => ext,
-                    _ => {
-                        return Err(ColumnQError::InvalidUri(format!(
-                            "unsupported extension in uri: {}",
-                            uri
-                        )));
+                match Path::new(uri).extension().and_then(OsStr::to_str) {
+                    Some(ext) => match ext {
+                        "csv" | "json" | "parquet" | "ndjson" | "arrow" | "arrows" => ext,
+                        _ => {
+                            return Err(ColumnQError::InvalidUri(format!(
+                                "unsupported extension in uri: {}",
+                                uri
+                            )));
+                        }
+                    },
+                    None => {
+                        // database sources doesn't have suffix extension, parse scheme instead
+                        match TableSource::parse_option(&self.io_source) {
+                            Some(TableLoadOption::mysql {}) => "mysql",
+                            Some(TableLoadOption::sqlite {}) => "sqlite",
+                            Some(TableLoadOption::postgres {}) => "postgres",
+                            _ => {
+                                return Err(ColumnQError::InvalidUri(format!(
+                                    "unsupported extension in uri: {}",
+                                    uri
+                                )));
+                            }
+                        }
                     }
                 }
             }
@@ -472,6 +478,9 @@ pub async fn load(t: &TableSource) -> Result<Arc<dyn TableProvider>, ColumnQErro
             "parquet" => parquet::to_datafusion_table(t).await?,
             "arrow" => Arc::new(arrow_ipc_file::to_mem_table(t).await?),
             "arrows" => Arc::new(arrow_ipc_stream::to_mem_table(t).await?),
+            "mysql" => Arc::new(database::DatabaseLoader::MySQL.to_mem_table(t)?),
+            "sqlite" => Arc::new(database::DatabaseLoader::SQLite.to_mem_table(t)?),
+            "postgresql" => Arc::new(database::DatabaseLoader::Postgres.to_mem_table(t)?),
             ext => {
                 return Err(ColumnQError::InvalidUri(format!(
                     "failed to register `{}` as table `{}`, unsupported table format `{}`",