問(wèn)題描述
我不小心編碼了 SELECT $FOO.. 并得到錯(cuò)誤無(wú)效偽列$FOO".
I accidentally coded SELECT $FOO.. and got the error "Invalid pseudocolumn "$FOO".
我找不到他們的任何文檔.這是我應(yīng)該知道的嗎?
I can't find any documentation for them. Is it something I should know?
這是一個(gè) MS SQL Server 特定問(wèn)題.
this is a MS SQL Server specific question.
推薦答案
偽列是實(shí)際列的符號(hào)別名，具有特殊屬性，例如，$IDENTITY 是分配了 IDENTITY 的列的別名，$ROWGUID 表示分配了 ROWGUIDCOL 的列.它用于內(nèi)部管道腳本.
Pseudocolumns are symbolic aliases for actual columns, that have special properties, for example, $IDENTITY is an alias for the column that has the IDENTITY assigned, $ROWGUID for the column with ROWGUIDCOL assigned. It's used for the internal plumbing scripts.
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