摘要:
JDBC查询优化分析:现有以下查询语句: String sql1 = "select * from userinfo";// 创建语句 String sql2 = "select count(*) from userinfo";// 创建语句 String sql3 = "select count(0) from userinfo";// 创建语句 String sql4 = "select username from userinfo";// 创建语句经过试验得出以下结论:select 子句为*时耗时最长,相当于 阅读全文
摘要:
出错信息:java.sql.SQLException: Incorrect string value: '\xE4\xBD\xA0\xE5\xA5\xBD' for column 'username' at row 1 at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1055) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956) at com.mysql.jdbc.MysqlIO.checkErrorPacket( 阅读全文