Data duplication may make your SELECT queries easier to write, but you can very easily end up with data integrity issues. FROM Tickets INNER JOIN Ticket Templates ON Tickets. So when might you need to copy data from one table to another? Consider a help desk application that allows support staff to create support tickets, where each ticket in the system exists as a record in the Tickets table. To ease data entry, let's say that administrative users can create "ticket templates," which pre-define the values for a number of ticket data points that are stored in a table named Ticket Templates. Applying a template to an existing ticket would require that the existing record in the Tickets table have its non-set data points assigned to the corresponding default values of the selected template. When you design relational expressions, you have to decide whether you want a single row to match multiple rows (in a one-to-many—1: M—relationship) or you want many rows to match a single row in the joined table (i.e., you want to update all rows).In a 1: M relationship, SQL Server always uses the last row it finds for the update.
If the table you're updating appears more than once in the FROM clause, only one reference to the table can omit a table alias; all other references to the table must include a table alias.
Presume that the Tickets table has a Ticket Template Id field that indicates what template is to be applied to the ticket.
Once this value has been assigned, the following UPDATE statement could be executed to copy the template's pre-defined values to the non-assigned data points in the Tickets table: UPDATE Tickets SET Priority Id = ISNULL(Tickets.
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How can I update three columns in table A from three columns in table B in one UPDATE statement?