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In SQL, how do I work with a table that has to have many (20+) foreign keys?

It is called a link table:




This is how you usually store many-to-many relations in a relational database.

Categories : SQL

Related to : In SQL, how do I work with a table that has to have many (20+) foreign keys?
Selecting elements from a foreign table matching foreign key?
Join the table as usual, and use MySQL's CONCAT or CONCAT_WS functions to concatenate the fields, such as: SELECT h.*, CONCAT_WS(' ', e.employee_firstname, employee_lastname) as employee FROM HOURS h INNER JOIN EMPLOYEE e ON e.employee-num = h.EMPLOYEE_employee_Num

Categories : Mysql
How does FOREIGN KEY references from one table to two table?
This is a common SQL Anti-Pattern. You should change your table structures so that your Material and Code of SemiProduct tables have a column that is a foreign key to the BOOM_Details table. That way you can always join between the tables as needed. So instead of a field in BOOM_Details that could point to either of the two tables, have a field in both of the tables that contains the primary ke

Categories : SQL
Several foreign keys in a table
Some reasons: it is sometimes easier to manage your data; when a specific value changes, you will only have to change it in one place: 'the small table' and not in many records of 'the big table'; it may be possible to use data in several places; it may take up less space; it may be faster; Are you really not able to reduce the number of columns? If you show us the table with some example dat

Categories : Mysql
Select each row of table except where the id is not the maximum value for a given foreign key
Something like this should work; SELECT respondent_id, MAX(id) as id FROM form_letters group by respondent_id MySQL fiddle:!2/5c4dc0/2

Categories : Mysql
sql create table same primary & foreign key
Yes we can. create table partner ( partner_id INTEGER NOT NULL PRIMARY KEY) create table personal_partner ( partner_id INTEGER NOT NULL PRIMARY KEY FOREIGN KEY REFERENCES partner(partner_id))

Categories : SQL
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