alter

This will seem rudimentary but I can't find a concise example online that matches up. I have three fields; m1 , m2 , and m3 . I need to create a column or field that is the average of them three. The calculated field would be titled employment. Would the following code be suffice? ALTER TABLE dbo.tablename ADD Employment AS Select ((m1+m2+m3)/3) Sample data m1 20 20 30 m2 15 17 25 m3 60 77 13 desired result. Name m1 m2 m3 Employment Auto body 20 20 30 23 Auto Parts 15 17 25 19 Auto Sales 60 77 13 50 You are very close, it's called Computed Column https://technet.microsoft.com/en-us/library

I try to add a column in a table with swift. my code : connect_db(); adddbfield("mynewfield","mytable"); . func connect_db() -> Bool { let sDBPath=<is correctly set>; if sqlite3_open(sDBPath, &db) != SQLITE_OK { println("Failed to open db") return false; }else{ return true; } } . func adddbfield(sFieldName:String, sTable:String) -> Bool { var bReturn:Bool=false; var sSQL="ALTER TABLE " + sTable + " ADD COLUMN " + sFieldName + " INTEGER DEFAULT -1"; var statement:COpaquePointer = nil if sqlite3_prepare_v2(db, sSQL, -1, &statement, nil) != SQLITE_OK { println("Failed to prepare statement") }else

Is there a way to rename a column on an InnoDB table without a major alter? The table is pretty big and I want to avoid major downtime. Renaming a column (with ALTER TABLE ... CHANGE COLUMN ) unfortunately requires MySQL to run a full table copy. Check out pt-online-schema-change . This helps you to make many types of ALTER changes to a table without locking the whole table for the duration of the ALTER. You can continue to read and write the original table while it's copying the data into the new table. Changes are captured and applied to the new table through triggers. Example: pt-online

I am developing a website using Spring+JPA+Hibernate. In the persistence configuration (JPA+Hibernate) I'm setting the HibernateJpaVendorAdapter's generateDdl attribute to true and in fact new entities correctly create the new table in the DB. Once the table has been created, though, if I add an attribute to the entity, I'm expecting the HibernateJpaVendorAdapter to alter the table and add the column as well. This is not happening and it's strange because in the Java AbstractJpaVendorAdapter's setGenerateDdl method documentation there is: "Set whether to generate DDL after the

How to alter an existing table in MySQL, setting foreign key to another table, using the command line? You have to drop existing foreign key and create another one. For example like this: ALTER TABLE my_table DROP FOREIGN KEY my_key; ALTER TABLE my_table ADD CONSTRAINT my_key FOREIGN KEY ('some_id') REFERENCES some_new_table ('some_other_id') ON UPDATE CASCADE ON DELETE CASCADE; Execute help alter table at mysql command prompt and the output is very much self explanatory. Look for add constraint with foreign key clause and apply it on your table. mysql> help alter table Name: 'ALTER TABLE'