Granted, the speed and disk space differences between the two types may be "Advanced MySQL," for more information), CHAR columns are faster to Unless you are using the InnoDB table types (see Chapter 11, VARCHAR columns tend to take up less disk space. Conversely, VARCHAR strings will be only as That anything stored as a CHAR will always be stored as a string the length of Strings and can be set with a fixed maximum length. There is some debate as to the merits of these two similar types. This is trueįor any field in which the length is set (CHAR, VARCHAR, INT, etc.). Into a CHAR(2) field, the final three characters will be truncated. You should keep in mind that if you insert a string five characters long Largest a number such as Client ID could be is in the hundreds, set the columnĪs an unsigned three-digit SMALLINT (allowing for up to 999 values). Value, based upon what the largest possible input could be. The size of any field should be restricted to the smallest possible Variable-length fields (such as VARCHAR), but they also take up more disk space. Get better results if you store them as numbers and address the formattingĬhoose the most appropriate subtype for eachįor improved performance, keep in mind two considerations:įixed-length fields (such as CHAR) are generally faster than ZIP codes and dollar amounts should be text fields if you include theirĬorresponding punctuation (dollar signs, commas, and hyphens), but you'll This is normally an easy and obvious step. ![]() Identify whether a column should be a text, Supported by other databases, and their usage undermines normalization. There are two caveats with ENUM and SET: These types are not Possible several thousand values, while SET allows for several of up to 64 There are also two extensions of the TEXT types that result in aĭifferent behavior≾NUM and SETwhich allow you to define a series ofĪcceptable values when creating the table. TIME fields without modification, so you need not worry too much about their Types have all sorts of unique behaviors, which are documented in the manual at ![]() Padded with zeroes (ZEROFILLs are also automatically UNSIGNED). Zeroor be defined as ZEROFILL, which means that any extra room will be The number types can be UNSIGNEDlimiting the column to positive numbers or Parentheses, while parentheses themselves indicate required arguments). ![]() Their size (the square brackets,, indicate an optional parameter to be put in Many of the types can take an optional Length attribute, limiting ![]() Like ENUM except that each column can have more than Short for enumeration, which means that each column In the format of YYYYMMDDHHMMSS acceptable range ends Or 0 to 18,446,744,073,709,551,615 unsigned.Ī small number with a floating decimal point.Ī large number with a floating decimal point.Ī DOUBLE stored as a string, allowing for a fixed decimal Range of -128 to 127 or 0 to 255 unsigned. A fixed-length field from 0 to 255 characters long.Ī string with a maximum length of 255 characters.Ī string with a maximum length of 65,535 characters.Ī string with a maximum length of 16,777,215 characters.Ī string with a maximum length of 4,294,967,295 characters.
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