If classes ‘Math’ or ‘Biology’ have flag is NULL or = 0, we need to left join with the first appeared (according to the date) classes ‘Literature’ or ‘English Literature’ from the below. If classes ‘Math’ or ‘Biology’ have flag = 1 then w…
Tag: left-join
How to differentiate between no rows and foreign key reference not existing?
My users table contains Alice, Bob and Charles. Alice and Bob have a 3 and 2 fruits respectively. Charles has none. A relationship is established using a foreign key constraint foreign key (user_id) references users (id) and a unique (user_id, name) constraint, allowing zero or one fruit per user. Charles doe…
PostgreSQL subquery COUNT fails when the subquery is joined more than once
I have 2 tables: Table class: Table class_event, where I store events related to classes, such as “started” and “ended”. I need a query the amount of times each class has been started and ended. This works: But when I do exactly the same to get the amount of ended classes it shows inco…
expected that this query will not output 0 values, but it does [closed]
Closed. This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed last month. Improve this question I expected that this query will not output 0 values, but it does. I thought that and (……
Getting different results from Subquery and JOIN which seem to be the same
I’m doing a challenge problem on DataCamp. It uses two tables, “economies” which contains economic information by country code, and “countries” which contains general country information by country code. The challenge is: Get country code, inflation rate, and unemployment rate in…
Can’t do Multiple Left Joins SQL Select (ODBC)
When I run the following SQL select statement with two left joins: I get the following error message in Excel VBA: “Run-time error ‘5’: Invalid procedure call or argument” When I run that exact same SQL without the left joins, it works without issue. I know the first SQL statement abov…
Join count query into one
I have two very simple count queries that I would like to join into one. To clarify the situation I will add the tables I got: Book isbn author 1111 GB 2222 DC 3333 RL Author code Name GB George B. KL Kyle L. DC Donald C. RL Roland L. Coauthor name isbn KL 1111 GB 2222 GB 3333 And
Include zero counts for grouping date ranged based SQL query
I’m trying to group and order the number of sales made in each day from a single ‘sales’ table with a created_at column and an id column. Each of the records might be created through out the day at any time. I’ve managed to do this with the following query: However, the days with 0 sal…
Take maximum time during update left join mysql
I am doing an update left join on ID and receiver. How can I make the query to pick the record with max time taken? Expected output : Answer I have added another column (id_primary) in right_table. To get the maximum use this subquery (select id_primary from right_table order by time_taken desc limit 1) at en…
What will be the output of the left join? [closed]
Closed. This question needs debugging details. It is not currently accepting answers. Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question. Closed 8 months ago. Improve this question I ha…