Question

How can i redesign the following query to avoid errors :

String sqlQueryToMakeTable = "create table " + UserEmail + 
                                        "(" +
                                           "NameOfThePhoto varchar(255)," + 
                                            "Caption varchar(255)" +
                                         ")";
// UserEmail is of type String

UserEmail is of the form [e-mail] and when i execute the query i get these errors :

java.sql.SQLSyntaxErrorException: Lexical error at line 1, column 18.  Encountered: "@" (64), after : "".
at org.apache.derby.client.am.SQLExceptionFactory40.getSQLException(Unknown Source)
at org.apache.derby.client.am.SqlException.getSQLException(Unknown Source)
at org.apache.derby.client.am.Connection.prepareStatement(Unknown Source)
at com.sun.gjc.spi.base.ConnectionHolder.prepareStatement(ConnectionHolder.java:562)
at com.sun.gjc.spi.jdbc40.ConnectionWrapper40.prepareCachedStatement(ConnectionWrapper40.java:255)
at com.sun.gjc.spi.jdbc40.ConnectionWrapper40.prepareCachedStatement(ConnectionWrapper40.java:52)
at com.sun.gjc.spi.ManagedConnection.prepareCachedStatement(ManagedConnection.java:964)
    .....

I understand the reason for exception. I run this query directly by placing the email address in the double quotes but what do i do here ?

EDIT Can’t we have @ in table name ?

Answer 1

Most databases permit arbitrary characters in table names as long as you enclose them in the correct quotes for the DB. For example,

For MySQL:

"create table `" + UserEmail + "` " +

For DB2:

"create table \"" + UserEmail + "\" " +

For SQL Server:

"create table [" + UserEmail + "] " +

For Derby it looks like double quotes might work, like with DB2: http://db.apache.org/derby/docs/10.0/manuals/reference/sqlj08.html

Then again, why are you creating a table for each user??

Update: The usual approach is having a single table of captions that also contains some data that can be used to identify the user. For example:

CREATE TABLE PhotoCaptions (
    UserEmail      varchar(255),
    NameOfThePhoto varchar(255),
    Caption        varchar(255)
)

Then, to find the caption for a particular photo of a particular user, you would use a query like this:

SELECT Caption FROM PhotoCaptions 
WHERE UserEmail = 'email' AND NameOfThePhoto = 'photoname'