如何检查 Snowflake 中的表是否为空并获得响应 - Java，SpringBoot

Question

I am using Snowflake database with Spring Boot in my project.

I have written a query in Java that queries the Snowflake temporary table and then copies that data in CVS format to S3.

Everything works fine until there is a user with no Snowflake data. Then the temporary table that was created is empty and no data is being copied in S3 which gives an error from S3 that objectKey is not found

So I was thinking to first create temporary table and then to check it if is empty. If is not empty, copy data to S3 if it is, return error.

I have this code for creating temporary table

public void getUser(String userId, String dbName) {

String q = "CREATE TEMPORARY TABLE \"TEST_DATABASE\".\"PUBLIC\".\"USER_TABLE_TEMP\" AS SELECT \"USERID\", \"FIRSTNAME\", \"LASTNAME\" from \"TEST_DATABASE\".\"PUBLIC\".\"USER\"";

jdbcTemplatePerBrand.values().forEach(tab -> tab.query(q, s -> {}));

}

Then I was thinking to add this part of code to check if table is empty:

String ifTableEmpty = "SELECT CASE WHEN EXISTS(SELECT 1 FROM \"TEST_DATABASE\".\"PUBLIC\".\"USER_TABLE_TEMP\") THEN 0 ELSE 1 END AS IsEmpty;\n";

jdbcTemplatePerBrand.get(brandAfterMigration).query(ifTableEmpty, s -> {});

if(ifTableEmpty.equals("0")){
 System.out.println("");
}

From above query I am not getting any result in way of 0 or 1 (Which I would like).

When I run a query to check if the table is empty in Snowflake, I get this result:

But I don't know how to get that result back to my code.

Answer 1

You can query the INFORMATION_SCHEMA tables:

SELECT ROW_COUNT
    FROM INFORMATION_SCHEMA.TABLES
   WHERE TABLE_SCHEMA = '<schema_name>'
     AND TABLE_NAME = '<table_name>';

Or use SHOW TABLES and get the result using result_scan:

SHOW TABLES LIKE 'pattern';

SELECT rows
  FROM TABLE (result_scan (last_query_id ()));

Reference: INFORMATION SCHEMA.TABLES , SHOW TABLES , RESULT_SCAN