Sqlobject update

SQLObject already has a tool for the job, sqlobject-admin. There are instructions on how to use it, but I found them unsatisfactory. So here is how I use sqlobject-admin to do migrations. In that case, bear in mind that tg-admin just simplifies the job for you by adding various standard parameters, but apart from that, the idea stays the same.

On linux machines it should be almost the same, but might require tweaking. You can change it to whatever you want. Starting to use sqlobject-admin Sqlobject-admin has quite a bit of bureaucracy to go through before you get everything to work right. For a simple project, I cheat i. Create a directory in your project called sqlobject-history b. The reason for this: the memory always faster than the tempdb database because the tempdb database uses the disk resources.

Now, if we go back to our position, the MERGE statement can be used as an alternative method for updating data in a table with those in another table. In this method, the reference table can be thought of as a source table and the target table will be the table to be updated. The following query can be an example of this usage method.

We have typed the Persons table after the MERGE statement because it is our target table, which we want to update, and we gave Per alias to it in order to use the rest of the query.

With the help of this syntax, the join condition is defined between the target and source table. In this last line of the query, we chose the manipulation method for the matched rows.

Finally, we added the semicolon ; sign because the MERGE statements must end with the semicolon signs. The major characteristic of the subquery is, they can only be executed with the external query.

The noticeable difference in this method is, it might be a convenient way to update one column for the tables that have a small number of the rows. Now we will execute the following query and then will analyze it. After the execution of the update from a select statement the output of the table will be as below;. As we can see, the PersonCityName column data of the Persons table have been updated with the City column data of the AddressList table for the matched records for the PersonId column.

Regarding this method, we should underline the following significant points. If the subquery finds more than one matched row, the update query will return an error, as shown below:. In this article, we learned to update the data in a table with the data where they are contained in other tables.

PersonId INT. PersonName , PersonLastName. N 'Salvador' , N 'Williams' ,. N 'Lawrence' , N 'Brown' ,. N 'Gilbert' , N 'Jones' ,. N 'Ernest' , N 'Smith' ,. N 'Jorge' , N 'Johnson'. This can also be used to change the column to NULL if the column has no default and is defined to allow null values. Only columns of varchar max , nvarchar max , or varbinary max can be specified with this clause. Offset is a zero-based ordinal byte position, is bigint , and cannot be a negative number.

If Offset plus Length exceeds the end of the underlying value in the column, the deletion occurs up to the last character of the value. Length is the length of the section in the column, starting from Offset , that is replaced by expression. Length is bigint and cannot be a negative number.

If the object being updated is the same as the object in the FROM clause and there is only one reference to the object in the FROM clause, an object alias may or may not be specified. If the object being updated appears more than one time in the FROM clause, one, and only one, reference to the object must not specify a table alias. All other references to the object in the FROM clause must include an object alias.

In particular, filter or join conditions applied on the result of one of those calls have no effect on the results of the other. The update operation occurs at the current position of the cursor. The search condition can also be the condition upon which a join is based.

There is no limit to the number of predicates that can be included in a search condition. A searched update modifies multiple rows when the search condition does not uniquely identify a single row. The cursor must allow updates.

Use caution when specifying the FROM clause to provide the criteria for the update operation. It is undefined which row from Table2 is to be used to update the row in Table1. Avoid using these hints in this context in new development work, and plan to modify applications that currently use them.

All char and nchar columns are right-padded to the defined length. These strings are truncated to an empty string. This can be configured in ODBC data sources or by setting connection attributes or properties. Modifying a text , ntext , or image column with UPDATE initializes the column, assigns a valid text pointer to it, and allocates at least one data page, unless the column is being updated with NULL.

If the UPDATE statement could change more than one row while updating both the clustering key and one or more text , ntext , or image columns, the partial update to these columns is executed as a full replacement of the values. Avoid using these data types in new development work, and plan to modify applications that currently use them. Use nvarchar max , varchar max , and varbinary max instead.

Use the. WRITE expression , Offset , Length clause to perform a partial or full update of varchar max , nvarchar max , and varbinary max data types. For example, a partial update of a varchar max column might delete or modify only the first bytes of the column characters if using ASCII characters , whereas a full update would delete or modify all the data in the column. WRITE updates that insert or append new data are minimally logged if the database recovery model is set to bulk-logged or simple.

Minimal logging is not used when existing values are updated. You cannot use the. Offset and Length are specified in bytes for varbinary and varchar data types and in byte-pairs for the nvarchar data type. For best performance, we recommend that data be inserted or updated in chunk sizes that are multiples of bytes. If the column modified by the. See example R that follows. To achieve the same functionality of. Supplying a value in a SQL Server system data type, as long as the user-defined type supports implicit or explicit conversion from that type.

The following example shows how to update a value in a column of user-defined type Point , by explicitly converting from a string. Invoking a method, marked as a mutator, of the user-defined type, to perform the update. The following example invokes a mutator method of type Point named SetXY. This updates the state of the instance of the type.

SQL Server returns an error if a mutator method is invoked on a Transact-SQL null value, or if a new value produced by a mutator method is null. Modifying the value of a registered property or public data member of the user-defined type. The expression supplying the value must be implicitly convertible to the type of the property. The following example modifies the value of property X of user-defined type Point.

To modify different properties of the same user-defined type column, issue multiple UPDATE statements, or invoke a mutator method of the type. However, a large amount of data is more efficiently streamed into a file by using Win32 interfaces.