How to update records in existing column using Spring JPA?-CodePudding

I am new to Java and spring. I have an existing database and table. I just wanted to update the records in the existing table. I have created a class and marked it with @entity annotation and I have spring.jpa.hibernate.auto-ddl set to update in application.properties.

But when I run my program it is creating new columns in the database. I don't want new columns to be added. Just wanted to map the table to the class and update existing records in the table.

Also, my table has 4 columns of which one has not null constraint on it. So when I run the program it's giving me an error saying "ALTER TABLE only allows columns to be added that can contain nulls, or have a DEFAULT definition specified, or a column being added is an identity, or timestamp column or alternatively if none of the previous conditions are satisfied the table must be empty to allow the addition of this column. Column brand_id cannot be added to a not empty table TableName because it does not satisfy these conditions." I could see on the console that it's executing alter table add column command.

Column names in the table are brandId, advanceDescription, and Aliases.

@Entity 
Public class TableName { 

    @Id 
    private int recid;
    
    private int brandId; 
    private String advanceDescription; 
    private String aliases; 
}

And the newly added column name in the table is advance_description.

CodePudding user response：

If I understand correctly, you don't want to change the schema of the table. Just add new data to it. To do so you need to disable auto-ddl and set it to none:
spring.jpa.hibernate.auto-ddl=none

Now the second problem is mismatched column names. Try changing your entity definition by setting a matching column name for each field. You can do it by using @Column(name="columnName") annotation. With the provided data it should be something like this:

@Entity 
public class TableName { 

    @Id 
    private int recid;
    
    @Column(name="brandId")
    private int brandId; 
    @Column(name="advance_description")
    private String advanceDescription; 
    @Column(name="Aliases")
    private String aliases; 
}

CodePudding user response：

Please try show create table tableName command on db.
it will give you the schema of your table like 
 CREATE TABLE `tableName` (
  `recid` int(11),
  `brand_id` int(11) unsigned NOT NULL,
  `advance_description` text,
  `aliases` text,
PRIMARY KEY (`recid`),
)

@Entity 
@Table("tableName")
public class TableName { 

    @Id 
    private int recid;
    
    @Column(name="brand_id")
    private int brandId; 
    @Column(name="advance_description")
    private String advanceDescription; 
    @Column(name="aliases")
    private String aliases; 

}

i.e. now you can see from the db command you will able to see that your table have brand_id field so you want to map brand_id field in your TableName.class with brandId field so in that case you have to add @Column(name = "brand_id) onto your brandId field i.e. in db field is brand_id but in java I want to map brand_id field to brandId.

This applicable to all column. Check for rec_id,advance_description and aliases too.