WMS Industries Interview Questions and Answers

select * from table limit 100 is faster

• Using 'select * from table' retrieves all rows from the table, which can be slower if the table is large

• Using 'select * from table limit 100' limits the number of rows retrieved, making it faster

• Limiting the number of rows fetched can improve query performance

GCP offers different storage classes for varying performance and cost requirements.

• Standard Storage: for frequently accessed data

• Nearline Storage: for data accessed less frequently

• Coldline Storage: for data accessed very infrequently

• Archive Storage: for data stored for long-term retention

SQL optimization techniques focus on improving query performance by reducing execution time and resource usage.

• Use indexes to speed up data retrieval

• Avoid using SELECT * and instead specify only the columns needed

• Optimize joins by using appropriate join types and conditions

• Limit the use of subqueries and instead use JOINs where possible

• Use EXPLAIN to analyze query execution plans and identify bottlenecks

SCD stands for Slowly Changing Dimension and Merge is a SQL operation used to update or insert data in BigQuery.

• SCD is used to track changes to data over time in a data warehouse

• Merge in BigQuery is used to perform insert, update, or delete operations in a single statement

• Example: MERGE INTO target_table USING source_table ON condition WHEN MATCHED THEN UPDATE SET col1 = value1 WHEN NOT MATCHED THEN INSERT (col1, col2) VALUES (value1, value2)

Dataflow function to split sentence

• Use the Split transform in Dataflow to split the sentence into words

• Apply ParDo function to process each word individually

• Use regular expressions to handle punctuation and special characters