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The problem was nobody knew for sure how much time this thing would need to complete. Well, we can find out how much progress it has made so far to make an educated guess:. This would tell us how many times the outer cursor has looped already.
It returned The two statement approach makes it easier to understand the conversion logic. This batch took approximately 17 hours to complete. Between the statement, I also put the database into simple recovery mode and added appropriate indexes to the temp table. 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. You cannot use. If an update to a row violates a constraint or rule, violates the NULL setting for the column, or the new value is an incompatible data type, the statement is canceled, an error is returned, and no records are updated.
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