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I want to save some sequence of digits, which may be a number (eg 12345, 1230) or not (eg 00123, 0120). Which type of column is the most effective (by memory, by indexing speed) for that purpose?

Also, I need to store strings of characters from specially defined alphabet (eg "digits and comma" or "digits and english letters and dots and commas"). How to effectively do this?

Can I set limits on CHAR/VARCHAR type of a column to reduce the memory size it takes?

Kirk Beard
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WallOfBytes
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2 Answers2

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This is no different from any string column which implies varchar/text type.

VARCHAR(n) takes care of storage dynamically.

Reference here.

For constraining allowed symbols you could use CHECK constraints, but they don't work in MySQL so a workaround is to use trigger and define accepted characters there. See this question. You could use REGEXP function to define your allowed alphabet.

Kamil Gosciminski
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For sql you can go with

varchar() and if your using POSTgreSQL you can make use of something known as citext

Chetan_Vasudevan
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