Expected one result (or null) to be returned by selectOne(), but found: 3 at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultS qlSession.java:70) selectList 可以查询一条或多条记录。 1.6.7 SqlSession；使用完毕就要关闭它。通常把这个关闭操作放到 finally 块中以 确保每次都能执行关闭。如下： SqlSession session = sqlSessionFactory.openSession(); try { // do work } finally { session.close(); } 2.3 原始 Dao 开发方式 原始 Dao 开发方法需要程序员编写 Dao 接口和 Dao Exception { SqlSession session = sqlSessionFactory.openSession(); User user = null; try { //通过sqlsession调用selectOne方法获取一条结果集 //参数1：指定定义的statement的id,参数2：指定向statement中传递的参 数 user = session.selectOne("test.findUserById"

can invoke the ‘insert’ mapped query using Java API as shown below − //Assume session is an SqlSession object. session.insert("Student.insert", student); Update To update values of an existing record You can invoke the update mapped query using Java API as shown below − //Assume session is an SqlSession object. session.update("Student.update",student); Delete To delete the values of an existing of SqlSession interface provided by MyBatis Java API as shown below − //Assume session is an SqlSession object. session.delete("Student.deleteById", 18); Select To retrieve data, ‘select’ mapper statement

Individual Session 526 Using SHA-256 Password Encryption 527 Setting the SHA-256 Password Hash Algorithm System-wide 527 Setting the SHA-256 Password Hash Algorithm for an Individual Session 527 VMware 777 Enabling GPORCA for a System 777 Enabling GPORCA for a Database 777 Enabling GPORCA for a Session or a Query 778 Collecting Root Partition Statistics 778 Running ANALYZE 778 GPORCA and Leaf Partition Hashing 1074 Time-based Authentication 1075 Accessing the Database 1075 Establishing a Database Session 1075 Supported Client Applications 1076 Greenplum Database Client Applications 1076 Connecting

572 Enabling GPORCA for a System 573 Enabling GPORCA for a Database 573 Enabling GPORCA for a Session or a Query 573 Collecting Root Partition Statistics 573 Running ANALYZE 574 GPORCA and Leaf Partition Parallel Retrieve Cursor 699 Listing a Parallel Retrieve Cursor’s Endpoints 699 Opening a Retrieve Session 700 Retrieving Data From the Endpoint 701 Waiting for Data Retrieval to Complete 701 Handling Closing the Cursor 702 Listing All Parallel Retrieve Cursors 702 Listing Segment-Specific Retrieve Session Information 703 VMware Greenplum 7 Documentation VMware by Broadcom 28 Limiting the Number of

Individual Session 497 Using SHA-256 Password Encryption 498 Setting the SHA-256 Password Hash Algorithm System-wide 498 Setting the SHA-256 Password Hash Algorithm for an Individual Session 498 Example 748 Enabling GPORCA for a System 748 Enabling GPORCA for a Database 748 Enabling GPORCA for a Session or a Query 749 Collecting Root Partition Statistics 749 Running ANALYZE 749 GPORCA and Leaf Partition Accessing the Database 1044 VMware Greenplum 6 Documentation VMware, Inc. 47 Establishing a Database Session 1044 Supported Client Applications 1045 Greenplum Database Client Applications 1045 Connecting

Individual Session 521 Using SHA-256 Password Encryption 522 Setting the SHA-256 Password Hash Algorithm System-wide 522 Setting the SHA-256 Password Hash Algorithm for an Individual Session 522 Example 768 Enabling GPORCA for a System 769 Enabling GPORCA for a Database 769 Enabling GPORCA for a Session or a Query 769 Collecting Root Partition Statistics 770 Running ANALYZE 770 GPORCA and Leaf Partition Hashing 1061 Time-based Authentication 1061 Accessing the Database 1061 Establishing a Database Session 1062 Supported Client Applications 1062 Greenplum Database Client Applications 1063 Connecting

Individual Session 501 Using SHA-256 Password Encryption 502 Setting the SHA-256 Password Hash Algorithm System-wide 502 Setting the SHA-256 Password Hash Algorithm for an Individual Session 502 Example 741 Enabling GPORCA for a System 742 Enabling GPORCA for a Database 742 Enabling GPORCA for a Session or a Query 742 Collecting Root Partition Statistics 742 Running ANALYZE 743 GPORCA and Leaf Partition Greenplum 6 Documentation VMware, Inc 45 Accessing the Database 1029 Establishing a Database Session 1030 Supported Client Applications 1030 Greenplum Database Client Applications 1030 Connecting

Individual Session 499 Using SHA-256 Password Encryption 500 Setting the SHA-256 Password Hash Algorithm System-wide 500 Setting the SHA-256 Password Hash Algorithm for an Individual Session 500 Example 740 Enabling GPORCA for a System 741 Enabling GPORCA for a Database 741 Enabling GPORCA for a Session or a Query 741 Collecting Root Partition Statistics 742 Running ANALYZE 742 GPORCA and Leaf Partition Hashing 1024 Time-based Authentication 1024 Accessing the Database 1024 Establishing a Database Session 1025 Supported Client Applications 1025 Greenplum Database Client Applications 1026 Connecting

Individual Session 424 Using SHA-256 Password Encryption 424 Setting the SHA-256 Password Hash Algorithm System-wide 424 Setting the SHA-256 Password Hash Algorithm for an Individual Session 425 Example 639 Enabling GPORCA for a System 640 Enabling GPORCA for a Database 640 Enabling GPORCA for a Session or a Query 640 Collecting Root Partition Statistics 640 Running ANALYZE 640 GPORCA and Leaf Partition Hashing 896 Time-based Authentication 896 Accessing the Database 896 Establishing a Database Session 896 Supported Client Applications 897 Greenplum Database Client Applications 897 Connecting with

Database 495 Stopping Client Processes 495 Accessing the Database 496 Establishing a Database Session 497 Supported Client Applications 497 Greenplum Database Client Applications 497 Connecting with Parameters at the Database Level 509 Setting Parameters at the Role Level 509 Setting Parameters in a Session 509 Viewing Server Configuration Parameter Settings 509 Configuration Parameter Categories 510 Viewing the Definition of an Object 609 Viewing Session Memory Usage Information 609 Creating the session_level_memory_consumption View 610 The session_level_memory_consumption View 610 Viewing Query