<select id="selectBlog" resultType="Blog"> select * from Blog where id = #{id} select> 对于这个简单的例子来说似乎有点小题大做了，但实际上它是非常轻量级的。在一个 XML selectBlog", 101); 你可能注意到这和使用完全限定名调用 Java 对象的方法是相似的，之所以这样做是有原因的。这个命名可以直接映射到在命名空间中 同名的 Mapper 类，并在已映射的 select 语句中的名字、参数和返回类型匹配成方法。这样你就可以向上面那样很容易地调用这个对 应 Mapper 接口的方法。不过让我们再看一遍下面的例子： BlogMapper mapper = session Java 注解。比如，上面的 XML 示例可被替换如下： package org.mybatis.example; public interface BlogMapper { @Select("SELECT * FROM blog WHERE id = #{id}") Blog selectBlog(int id); } 对于简单语句来说，注解使代码显得更加简洁，然而 Java

alhost:3306/mybatis?charac terEncoding=utf-8", "root", "mysql"); //定义sql语句 ?表示占位符 String sql = "select * from user where username = ?"; //获取预处理statement preparedStatement = connection.prepareStatement(sql); -- 根据id获取用户信息 --> <select id="findUserById" parameterType="int" resultType="cn.itcast.mybatis.po.User"> select * from user where id = #{id} select> <select id="findUserByUsername" parameterType="java.lang.String" resultType="cn.itcast.mybatis.po.User"> select * from user where username like '%${value}%' select> parameterType：定义输入到 sql 中的映射类型，#{id}表示使用 preparedstatement 设 置占位符号并将输入变量

mybatis_test.test1.userMapper"> <select id="getUser" parameterType="int" resultType="com.atguigu.mybatis_test.test1.User"> select * from users where id=#{id} select> 2.6. 在 conf.xml 文件中注册 2.7. 编写测试代码：执行定义的 select 语句 public class Test { public static void main(String[] args) throws IOException { String resource age=#{age} where id=#{id} <select id="selectUser" parameterType="int" resultType="com.atguigu.ibatis.bean.User"> select * from users where id=#{id} select> <select id="selectAllUsers" resultType="com

important file in MyBatis, which contains a set of statements to configure various SQL statements such as select, insert, update, and delete. These statements are known as Mapped Statements or Mapped SQL Statements delete("Student.deleteById", 18); Select To retrieve data, ‘select’ mapper statement is used. Following is the example of select mapped query to retrieve all the records in a table − <select id = "getAll" resultMap resultMap = "result"> SELECT * FROM STUDENT; select> You can retrieve the data returned by the select query using the method selectList. This method returns the data of the selected record in the form

my_avg(int4) (stype = avg_state, sfunc = avg_transfn, finalfunc = avg_finalfn) CREATE TABLE agg_data_2k AS SELECT g FROM generate_series(0, 1999) g; CREATE SCHEMA alt_nsp1; ALTER AGGREGATE alt_agg3(int) OWNER (template=simple) CREATE RULE def_view_test_ins AS ON INSERT TO def_view_test DO INSTEAD INSERT INTO def_test SELECT new.* ALTER TABLE alterlock SET (toast.autovacuum_enabled = off) CREATE PUBLICATION pub1 FOR TABLE my_avg(int4) (stype = avg_state, sfunc = avg_transfn, finalfunc = avg_finalfn) CREATE TABLE agg_data_2k AS SELECT g FROM generate_series(0, 1999) g; CREATE SCHEMA alt_nsp1; ALTER AGGREGATE alt_agg3(int) OWNER

my_avg(int4) (stype = avg_state, sfunc = avg_transfn, finalfunc = avg_finalfn) CREATE TABLE agg_data_2k AS SELECT g FROM generate_series(0, 1999) g; CREATE SCHEMA alt_nsp1; ALTER AGGREGATE alt_agg3(int) OWNER (template=simple) CREATE RULE def_view_test_ins AS ON INSERT TO def_view_test DO INSTEAD INSERT INTO def_test SELECT new.* ALTER TABLE alterlock SET (toast.autovacuum_enabled = off) CREATE PUBLICATION pub1 FOR TABLE my_avg(int4) (stype = avg_state, sfunc = avg_transfn, finalfunc = avg_finalfn) CREATE TABLE agg_data_2k AS SELECT g FROM generate_series(0, 1999) g; CREATE SCHEMA alt_nsp1; ALTER AGGREGATE alt_agg3(int) OWNER

correlating query, so the query efficiency will increase greatly. Take this one for example, if SQL is: SELECT i.* FROM t_order o JOIN t_order_item i ON o.order_id=i.order_id WHERE o. order_id in (10, 11); 4 SQLs in Cartesian product after routing: SELECT i.* FROM t_order_0 o JOIN t_order_item_0 i ON o.order_id=i.order_id WHERE o. order_id in (10, 11); SELECT i.* FROM t_order_0 o JOIN t_order_item_1 i order_id=i.order_id WHERE o. order_id in (10, 11); SELECT i.* FROM t_order_1 o JOIN t_order_item_0 i ON o.order_id=i.order_id WHERE o. order_id in (10, 11); SELECT i.* FROM t_order_1 o JOIN t_order_item_1 i

correlating query, so the query efficiency will increase greatly. Take this one for example, if SQL is: SELECT i.* FROM t_order o JOIN t_order_item i ON o.order_id=i.order_id WHERE o. order_id in (10, 11); after routing: SELECT i.* FROM t_order_0 o JOIN t_order_item_0 i ON o.order_id=i.order_id WHERE o. order_id in (10, 11); 4.2. Sharding 24 Apache ShardingSphere document, v5.0.0 SELECT i.* FROM t_order_0 order_id=i.order_id WHERE o. order_id in (10, 11); SELECT i.* FROM t_order_1 o JOIN t_order_item_0 i ON o.order_id=i.order_id WHERE o. order_id in (10, 11); SELECT i.* FROM t_order_1 o JOIN t_order_item_1 i

my_avg(int4) (stype = avg_state, sfunc = avg_transfn, finalfunc = avg_finalfn) CREATE TABLE agg_data_2k AS SELECT g FROM generate_series(0, 1999) g; CREATE SCHEMA alt_nsp1; ALTER AGGREGATE alt_agg3(int) OWNER (template=simple) CREATE RULE def_view_test_ins AS ON INSERT TO def_view_test DO INSTEAD INSERT INTO def_test SELECT new.* ALTER TABLE alterlock SET (toast.autovacuum_enabled = off) CREATE PUBLICATION pub1 FOR TABLE my_avg(int4) (stype = avg_state, sfunc = avg_transfn, finalfunc = avg_finalfn) CREATE TABLE agg_data_2k AS SELECT g FROM generate_series(0, 1999) g; CREATE SCHEMA alt_nsp1; ALTER AGGREGATE alt_agg3(int) OWNER

my_avg(int4) (stype = avg_state, sfunc = avg_transfn, finalfunc = avg_finalfn) CREATE TABLE agg_data_2k AS SELECT g FROM generate_series(0, 1999) g; CREATE SCHEMA alt_nsp1; ALTER AGGREGATE alt_agg3(int) OWNER (template=simple) CREATE RULE def_view_test_ins AS ON INSERT TO def_view_test DO INSTEAD INSERT INTO def_test SELECT new.* ALTER TABLE alterlock SET (toast.autovacuum_enabled = off) CREATE PUBLICATION pub1 FOR TABLE my_avg(int4) (stype = avg_state, sfunc = avg_transfn, finalfunc = avg_finalfn) CREATE TABLE agg_data_2k AS SELECT g FROM generate_series(0, 1999) g; CREATE SCHEMA alt_nsp1; ALTER AGGREGATE alt_agg3(int) OWNER