MyBatis Dynamic SQL

SQL statements in MyBatis can be dynamically generated and spelled with conditional judgments

1. Use if+where to spell SQL statements

　　

, use if to determine the spelling of SQL according to the parameters passed in

2. Using Trim+if to implement the spelling of SQL

　　

There are some properties in Trim:

"1" prefix: prefix

"2" prefixoverrides= "and | Or "Override the prefix to avoid occurrences of the and OR or

"3" suffix= "" suffix, and at the end of Trim plus

"4" suffixoverrides= "" suffix rewrite, in each if in the SQL statement after adding, to avoid unnecessary

3. Update with If+set (set will automatically ignore end,)

4. When a range operation is required, a foreach is usually used

Such as:

　　

Use the Foreach loop to facilitate the variable passed into the parameter list. Properties of foreach:

Collection= "": If the passed parameter is a number, write the Array, if the passed parameter is list, then write the list, if the incoming parameter is map, write the corresponding key name in the map

Item: Refers to the current object

Open: Start

Close: End

Separator: Delimiter

5. Use Choose (when,otherwise) similar to switch in Java

　　　　

Otherwise refers to other conditions

MyBatis Dynamic SQL