問題：
I'm trying to update the length of a varchar column from 255 characters to 500 without losing the contents.我試圖在不丟失內容的情況下將 varchar 列的長度從 255 個字符更新爲 500 個字符。 I've dropped and re-created tables before but I've never been exposed to the alter statement which is what I believe I need to use to do this.我之前刪除並重新創建了表，但我從未接觸過 alter 語句，我相信我需要使用它來執行此操作。 I found the documentation here: ALTER TABLE (Transfact-SQL) however I can't make heads or tails of it.我在這裏找到了文檔： ALTER TABLE (Transfact-SQL)但是我無法理解它。
I have the following so far (essentially nothing unfortunately):到目前爲止，我有以下內容（不幸的是，基本上沒有）：
alter table [progennet_dev].PROGEN.LE
alter column UR_VALUE_3
How do I approach this?我該如何處理？ Is there better documentation for this statement out there (I did some searches for an example statement but came up empty)?是否有關於此語句的更好的文檔（我搜索了一些示例語句，但結果爲空）？
解決方案：
參考一： https://en.stackoom.com/question/b2q5參考二： https://stackoom.com/question/b2q5