Updating Existing Data Change the foreman of the Polonia plant to Gaul, The command allows you to change existing data Update Volker in a table without deleting the record and re-entering it. Remove the foreman phone Update TABLENAME = number of the Polonia Set fieldname newvalue [,fieldname = newvalue] plant. Where condition keyword and clause are not optional Set To change multiple fields at once, separate each field and value with commas clause is optional, but if omitted all rows are Where changed. clause often dependent on primary key Where (though not required to be) To update a field value to Null, = Set fieldname Null No apostrophes, no Is New value can be a calculated value using any database fields. Note the MySQL Workbench prohibits Delete and Update commands that have a Where clause or don’t where the Where clause does NOT include the primary key. You can turn off this feature: EditPreferencesSQL Queries”Safe Updates” Or, you can enter the following MySQL command: set sql_safe_updates = 0; You can also update using fields from multiple tables by joining the tables or using subqueries. (Assume a inventoryvalue column has been added to tblinventory in Henry Books) update tblinventory i inner join tblbooks b on i.bookcode=b.bookcode set inventoryvalue = onhand * price; (Assume a totalonhand column has been added to tblbooks in Henry Books) Update tblbooks b Set totalonhand = (Select sum(onhand) from tblinventory i Where i.bookcode=b.bookcode);
Updating Existing Data The Update command allows you to change existing data in a table without deleting the record and re-entering it. Update TABLENAME Set fieldname = newvalue [,fieldname = newvalue] Where condition Set keyword and clause are not optional To change multiple fields at once, separate each field and value with commas Where clause is optional, but if omitted all rows are changed. Where clause often dependent on primary key (though not required to be) To update a field value to Null, Set fieldname = Null No apostrophes, no Is New value can be a calculated value using any database fields. Note the MySQL Workbench prohibits Delete and Update commands that don’t have a Where clause or where the Where clause does NOT include the primary key. You can turn off this feature: EditPreferencesSQL Queries”Safe Updates” Or, you can enter the following MySQL command: set sql_safe_updates = 0; Change the foreman of the Polonia plant to Gaul, Volker Remove the foreman phone number of the Polonia plant. You can also update using fields from multiple tables by joining the tables or using subqueries. (Assume a inventoryvalue column has been added to tblinventory in Henry Books) update tblinventory i inner join tblbooks b on i.bookcode=b.bookcode set inventoryvalue = onhand * price; (Assume a totalonhand column has been added to tblbooks in Henry Books) Update tblbooks b Set totalonhand = (Select sum(onhand) from tblinventory i Where i.bookcode=b.bookcode);
5%20-%20Updating%20Data%20&%20Structure.docx