此外，这些类型的sql语句对适当的索引和数据库设计最敏感，因此查看以下指示，获取实现最优性能的技巧。
Additionally, these kinds of SQL statements are the most sensitive to proper indexing and database design, so look to the following Pointers for tips for optimal performance.
我们编辑了 SQL 脚本文件，并更改了前两个 SQL 语句，以指示希望使用的数据库名称
We edited the SQL script file and changed the first two SQL statements to indicate the desired database name
if语句支持一个可选的else子句，指示当布尔表达式计算为False时应该处理的程序语句块。
The if statement supports an optional else clause that indicates a block of program statements that should be processed if the Boolean expression evaluates False.
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