Query mapping table information

Use Tablestore SDK for Java to query mapping table schemas, including field names, field types, primary keys, and nullability.

Prerequisites

Install the Tablestore SDK for Java and initialize a client.
Use Tablestore SDK for Java 5.13.0 or later.

Description

Call the sqlQuery method to execute a DESCRIBE statement and query the field schema of a mapping table.

SQLQueryResponse sqlQuery(SQLQueryRequest request)

The following example queries the field schema of the example_table mapping table and reads each item by field name.

SQLQueryRequest request =
        new SQLQueryRequest("DESCRIBE example_table");
SQLQueryResponse response = client.sqlQuery(request);

SQLResultSet resultSet = response.getSQLResultSet();
while (resultSet.hasNext()) {
    SQLRow row = resultSet.next();
    System.out.println(
            row.getString("Field") + ", "
                    + row.getString("Type") + ", "
                    + row.getString("Null") + ", "
                    + row.getString("Key") + ", "
                    + row.getString("Default") + ", "
                    + row.getString("Extra"));
}

Parameters

SQLQueryRequest contains the following parameter.

Name	Type	Description
query (required)	String	The `DESCRIBE <mapping_table_name>` statement to execute. `mapping_table_name` specifies the name of the mapping table.

Response

SQLQueryResponse contains the following fields related to the mapping table schema.

Field	Type	Description
`type`	SQLStatementType	Call `getSQLStatementType()` to obtain the SQL statement type. `SQL_DESCRIBE_TABLE` is returned for a `DESCRIBE` statement.
`rows`	ByteString	The serialized mapping table schema. Call `getSQLResultSet()` to obtain the parsed `SQLResultSet`.

Result set fields

Each row in the SQLResultSet represents a field in the mapping table and contains the following columns.

Field	Type	Description
`Field`	String	The field name.
`Type`	String	The SQL data type of the field.
`Null`	String	Indicates whether the field can be null. Valid values: `YES` and `NO`.
`Key`	String	The key type of the field. `PRI` indicates a primary key field.
`Default`	String	The default value of the field. If no default value is configured, `null` is returned.
`Extra`	String	Additional field information.