regexp to match AlphaNumeric with pattern

If alphanumeri开发者_开发技巧c all numbers can't be 9's.

If lengh of the string 7 must be 1 alpha + 6 numeric.

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UPDATED: For the first part

if alphanumeric all numbers can't be 9's

and seeing that A999999 is not possible. It should not match this

[a-zA-Z]{1,2}[^9]{6}

but it should match this.

[a-zA-Z]{1,2}[0-9]{6}