Standard SQL - CHAR to ASCII

Using standard SQL, SQL-92, how can I convert a character to an开发者_运维知识库 ASCII value?

In MySQL it's easy using the ascii() function, but SQL-92 doesn't have this.

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It appears the SQL-92 standard doesn't even mention ASCII at all.

As you say, each RDBMS vendor would have its own implementation how to convert char->ascii and ascii->char.

Most name this function ASCII().

• SQL Server ASCII
• Postgresql ASCII
• Oracle ASCII
• MySQL ASCII

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Create a lookup table with all the ASCII characters and their corresponding values -- there are only 127 of them -- and then just do SELECT [value] FROM [table] WHERE [character] = 'A' etc.