Concatenating Fields

最新推荐文章于 2022-06-22 11:43:43 发布

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本文介绍了在SQL中如何使用不同的操作符来拼接字符串。具体包括使用+或||符号进行拼接的方法，并说明了不同数据库管理系统(DBMS)的支持情况。此外，还介绍了如何使用SQL的RTRIM()函数去除字符串右侧的空白字符。

In SQL SELECT statements, you can concatenate columns using a special operator. Depending on which DBMS you are using, this can be a plus sign (+) or two pipes (||).

+ or ||? Access, SQL Server, and Sybase support + for concatenation. DB2, Oracle, PostgreSQL, and Sybase support ||. Refer to your DBMS documentation for more details.

|| is actually the preferred syntax, so more and more DBMSs are implementing support for it.

SELECT vend_name + ' (' + vend_country + ')'

FROM Vendors

ORDER BY vend_name;

Many databases (although not all) save text values padded to the column width. To return the data formatted properly, you must trim those padded spaces. This can be done using the SQL RTRIM() function

SELECT RTRIM(vend_name) + ' (' + RTRIM(vend_country) + ')'

FROM Vendors

ORDER BY vend_name;

The TRIM Functions Most DBMSs support RTRIM() (which, as just seen, trims the right side of a string), as well as LTRIM() (which trims the left side of a string), and TRIM() (which trims both the right and left).