字符串MSSQL 高效拼接字符串技巧（mssql 拼接）

String concatenation is a key skill for anyone working with strings, algorithms, and databases. MSSQL, in particular, provides some special features for string manipulation, including a special syntax for concatenating strings. In this tutorial, I’ll show you how to use this syntax to efficiently join strings in MSSQL.

MSSQL provides a couple of different methods for concatenating strings. The most straightforward approach is to use the native `+` operator. This operator is common among many programming languages, so it’s likely that you’re already familiar with it. To use the `+` operator in MSSQL, simply append each string to the one before it:

“`SQL

SELECT ‘string1’ + ‘string2’ + ‘string3;

This approach works well in simple cases, but it becomes inefficient when concatenating large numbers of strings. In these situations, it's better to use the `CONCAT` function, which takes an arbitrary number of strings as arguments:

```SQL
SELECT CONCAT('string1', 'string2', 'string3');

The `CONCAT` function is more efficient than the `+` operator because it processes multiple strings in a single operation. This makes it a better choice for joining large numbers of strings.

Finally, MSSQL also provides an `XMLPATH` clause for string concatenation. This clause produces a single string out of all values in a table or view column. To use the `XMLPATH` clause, you first need to create an `XML` type column in your table. Then, use the `FOR XML` clause to select all values into a single string:

“`SQL

SELECT col1

FROM mytable

FOR XML PATH(”)

The `XMLPATH` clause can be an effective way to join large numbers of strings, since it processes all values in a single operation. 

In conclusion, MSSQL provides several convenient options for joining strings. The `+` operator is a straightforward approach, while the `CONCAT` function is useful for joining large numbers of strings. The `XMLPATH` clause is also a quick way to join strings from a table or view column. With a little experience, you can use these approaches to quickly and efficiently join strings in MSSQL.