SQL/XML is good if you want results returned as sets and missing XML elements represented with nulls.
如果您希望将结果作为集合返回,且将丢失的 XML 元素表示为空,那么 SQL/XML 有优势。
SQL USES a small integer which contains a zero if the column is not null or -1 if the column contains nulls.
如果列不包含空值,则SQL使用一个包含一个0的小整数;反之则包含- 1。
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