MySQL Cookbook, 2nd Edition

Introduction

Like most types of data, string values can be compared for equality or inequality or relative ordering. However, strings have some additional features to consider:

• A string can be binary or nonbinary. Binary strings are used for raw data such as images, music files, or encrypted values. Nonbinary strings are used for character data such as text and are associated with a character set and collation (sorting order).

• A character set determines which characters are legal in a string. Collations can be chosen according to whether you need comparisons to be case-sensitive or case-insensitive, or to use the rules of a particular language.

• Data types for binary strings are BINARY, VARBINARY, and BLOB. Data types for nonbinary strings are CHAR, VARCHAR, and TEXT, each of which allows CHARACTER SET and COLLATE attributes. See Choosing a String Data Type for information about choosing data types for string columns.

• You can convert a binary string to a nonbinary string and vice versa, or convert a nonbinary string from one character set or collation to another.

• You can use a string in its entirety or extract substrings from it. Strings can be combined with other strings.

• You can apply pattern-matching operations to strings.

• FULLTEXT searching is available for efficient queries on large collections of text.

This chapter discusses how to use all those features, so that you can store, retrieve, and manipulate strings according to whatever requirements your applications have.

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