Problem description & analysis: The second and third fields of a certain database table are the starting year/month, and the ending year/month, respectively, in the format of “year M month”. Task: Now we need to add a calculated column TimePeriods: ...
Problem description & analysis: A certain database table records the execution status of a project, with multiple people participating in the project every day, and one person can participate in multiple tasks of the project in one day. Task: Now we...
Key Points It seems likely that mastering Flutter, Django-REST, and MySQL can lead to high-paying tech jobs, with salaries varying by location and experience. Research suggests starting with Python and Dart fundamentals, then learning Flutter for m...
Problem description & analysis: A certain table stores records of personnel from external sources entering and leaving a building by swiping their cards in recent days. When a person enters and exits a building, there are usually N pairs of records, ...
Problem description & analysis: A table stores events that occur for multiple accounts on multiple dates. Task: Now we need to find a pair of events that meet the criteria under each account, namely: event a with the earliest date, and event b with ...
Problem description & analysis: A certain table in the MS SQL database has a multi-level self-association structure, where the second field parent node ID is a foreign key pointing to the first field node ID of the table, and the third field is a zon...
Problem description & analysis: There is a transaction table for the asset accounts in the MS SQL database, with dates that are not consecutive. Task: Now we need to calculate the balance of each account for each month from January 2021 at the begin...
Problem description & analysis: The table mytable in the MS SQL database has one ConfirmationStarted and multiple Closed statuses for each ID. Task: Now we need to find the record closest to ConfirmationStarted among all the Closed records before Co...
SQL (Structured Query Language) is a powerful tool used for managing and manipulating databases. However, just like any other programming language, SQL can sometimes throw errors that can be tricky to resolve. Whether you are a beginner or an experie...
Problem description & analysis: The id and nbr of the MS SQL database table are grouping fields. After sorting the records within the group by time field dt, the order of 0 and 1 in the status field ‘status’ is different. Task: Now we need to genera...
