MySQLSyntaxErrorexception On Alter Table ...在MySQL Connector / J中转换为...

Question

使用MySQL-Connector-Java-5.1.28运行Ubuntu 14.04。

让我们创建一个表：

CREATE TABLE mytable (value1 VARCHAR(32000), value2 TEXT, value3 VARCHAR(1000), value4 VARCHAR(32000)) CHARACTER SET latin1 COLLATE latin1_swedish_ci;

.

通过stategy.execute（）失败地执行以下alter table语句，说“列长度太大.. * ”。

根据文档 alter table ...转换为。但是，请根据需要执行自动类型转换，以确保新列足够长，以将多个字符存储为原始列。 该声明确实在执行必要转换的本机MySQL客户端中运行。 我在JDBC中绊倒到JDBC中的错误，或者是预期这个行为吗？

ALTER TABLE mytable CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Column length too big for column 'value1' (max = 21845); use BLOB or TEXT instead
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.Util.getInstance(Util.java:386)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1054)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4237)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4169)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2617)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2778)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2819)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2768)
    at com.mysql.jdbc.StatementImpl.execute(StatementImpl.java:949)
    at com.mysql.jdbc.StatementImpl.execute(StatementImpl.java:795)
    at Main.main(Main.java:32)

.

Answer 1

In my previous response I have not taken into account CONVERT TO behavior, so I have tried your test, first using the mysql native client and all works fine, column are automatically converted, and then using a jdbc connector and actually I got the same error... but after some test and some research I have found the solution.

You have to add in your jdbc connection url the parameter jdbcCompliantTruncation and set it to false

jdbc:mysql://localhost/test?jdbcCompliantTruncation=false

Should the driver throw java.sql.DataTruncation exceptions when data is truncated as is required by the JDBC specification when connected to a server that supports warnings (MySQL 4.1.0 and newer)? This property has no effect if the server sql-mode includes STRICT_TRANS_TABLES.

Default: true

Source: 5.1 Driver/Datasource Class Names, URL Syntax and Configuration Properties for Connector/J

Running my java code using the above connection url the table mytable are correctly converted (I have tried only with an empty table):

mysql> desc mytable;
+--------+---------------+------+-----+---------+-------+
| Field  | Type          | Null | Key | Default | Extra |
+--------+---------------+------+-----+---------+-------+
| value1 | mediumtext    | YES  |     | NULL    |       |
| value2 | mediumtext    | YES  |     | NULL    |       |
| value3 | varchar(1000) | YES  |     | NULL    |       |
| value4 | mediumtext    | YES  |     | NULL    |       |
+--------+---------------+------+-----+---------+-------+

So, if the server runs without STRICT_TRANS_TABLES in sql_mode, ex:

mysql> show variables like 'sql_mode';
+---------------+------------------------+
| Variable_name | Value                  |
+---------------+------------------------+
| sql_mode      | NO_ENGINE_SUBSTITUTION |
+---------------+------------------------+

the jdbcCompliantTruncation=false cause the alignment of the behavior between server and jdbc client.