Does the outsourcing mall share one database or multiple databases?

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(suppose) I want to be a mall in the cup industry, and then sell the mall to various cup merchants. My personal idea is to be a general mall, sharing a backstage and a set of databases. If there is a merchant who wants to customize the page, he will be paid to make a foreground template for him alone. The problem now is to assume that a merchant wants to customize the background function and this function conflicts with other functions, what should I do if forced to add it will affect other users? no, no, no. In fact, the question can also be reduced to whether I share a set of programs and a database, or a roughly equivalent set of programs + independent databases.

Apr.11,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b3512f-2bf70.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3512f-2bf70.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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