SELF JOIN: en esta circunstancia, la misma tabla se especifica dos veces con dos alias diferentes para hacer coincidir los datos dentro de la misma tabla. ProductID, P. Name, P. ListPrice, P. Size, P. ModifiedDate, SOD. UnitPrice, SOD. OrderQty, SOD. I was curious as to whether the row by row would have been better because I presume the problem was cause becasuse someone was trying to update a contact I had in my batc as it would have looked at a contact one at a time?
Row by row better? Well, in the sense that if one fails the whole batch won't fail, but then you have no guarantee that all the contacts were updated.
That was my decision in the end to be honest, out of business hours. Worked out okay for this situation. I guess I was just thinking if one was foced to do it in business hours if this would be better or not. Gabriel P. For large tables, I usually do a hybrid of both But you want to do everything in your power to avoid doing 1 row per transaction. Not only will it take forever, but it will cause rampage in your transaction log. Even if you only did 5 or 20 rows per transaction, the amount of time and transaction log IO you use is cut down is pretty significant compared to only doing 1 row at time.
But for a table that is being used during business hours, the primary goal is to make sure each transaction still happens pretty instantaneous, so of course there is a limit to how many of rows you can include in each transaction.
Gabriel, that makes quite a lot of sense, I guess I could have broken my say 2, into blocks of perhaps, however, in that instance out hours makes more sense as it's not mission critical to be done instantly. Paul White. The batch approach is certainly more efficient for the update operation; that side of things has been well-covered in previous comments. Both batch and row-by-row queries feature hard-coded numeric values, which are presumably keys for the table concerned.
It is much more common to use a dynamic selection query, or to use keys from a table usually a temporary one. Listado 7. Como se hace en SQL para actualizar una fila o varias filas. Listado 8. Como se hace en VFP para borrar una fila. Listado 9. Como se hace en VFP para borrar varias filas. Listado Como se hace en VFP para borrar todas las filas de una tabla. Como se hace en SQL para borrar una o varias filas. Como se hace en SQL para borrar todas las filas de una tabla.
Como se hace en VFP para observar el contenido de una tabla. Como se hace en SQL para observar el contenido de una tabla. Entre ellos podemos mencionar:. Algunas de ellas. En SQL hay 4 comandos principales. Son llamados los cuatro grandes del SQL. Esos comandos son:. Vale la pena.
En general nadie tiene problemas por usar ese comando. Eso, tiene su parte buena y su parte mala. De todas maneras, en los 4 grandes no suelen existir diferencias muy notorias, las mayores diferencias suelen estar en el lenguaje empleado para escribir los triggers y los stored procedures.
Los triggers que se ejecutan antes se usan normalmente para validar datos. Puede ser la propia computadora o alguna otra computadora, tanto en una red local como en una red remota. Para que el Cliente pueda comunicarse con el Servidor y para que el Servidor pueda comunicarse con el Cliente , se necesita de un canal que los enlace.
FDB;" En el Listado 1.
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