91 | The attribute column name (EXCEPTION) is a reserved SQL-99 keyword.How do I fix this error/warning that Netbeans gives me? "The attribute column name (EXCEPTION ... but could be with other DBMS. To remove the warning, either rename your field (e.g. to exceptionText), or add a Column annotation that will map the name of the Java field to another name in the database: @Column(name |
89 | @Column length is not working.I am using objectdb 2.8.3, I have a Entity class with a column that is declared as @Column(unique = true, nullable = false, length = 16) but when i m trying to insert a string for that column ... so its very difficult to validate the column string length. Please find the below project and objectdb file |
88 | Order in WHERE Clause affects behaviour on DATE/DATETIME columnsQuick example: public class MyClass { @Column(name = "myText") String myText; @Temporal(TemporalType.TIMESTAMP) @Column(name = "myDate") Date myDate; } Now ... obviously makes a difference. The date column seems to be converted to a String |
88 | @Column( name = "columnName") doesn't work { @Id @GeneratedValue @Column(name = "KEY_ID") private long id; private Long timestamp; @ManyToOne @Column(name = "KEY_DESCRIPTOR") private AfwKeyDescriptor keyDescriptor; @OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL) @Column( name = "DATA_ITEMS |
88 | Adding new unique columnsWhat is the best practice for when you need to add a new unique column to an existing database? Simply adding the column with the @Unique annotation will result in "Attempt to reuse an existing value (null)", so the only option I can surmise is to add the column, update all existing entries |
87 | drop a column from tableHi, I want to drop one column from my database table suppose i have 3 column (id, name, address) now i want to drop address. then what will be the query or procedure.. Bimal Bimal kumar dalei Just ... But it physically present and logically it will not display. If a want to drop or delete a column |
87 | Index on a low cardinality column up queries." "An index on the gender column likely would not help because there's no value in an index on a low cardinality column. Meaning, there's not enough variety in the values for the index to provide any value." an index on a low cardinality column is generally not recommended as mentioned |
50 | SqlResultSetMapping.columnsAnnotation Element javax.persistence.SqlResultSetMapping ColumnResult[] columns Specifies the result set mapping to scalar values. Default value: {} Since: JPA 1.0 |
18 | javax.persistence.JoinColumn a column for joining an entity association or element collection. If the JoinColumn annotation itself is defaulted, a single join column is assumed and the default values apply. Example: @ManyToOne ... @JoinColumn(name="CUST_ID") // join column is in table for Order public Set |
17 | javax.persistence.MapKeyJoinColumn) Specifies a mapping to an entity that is a map key. The map key join column is in the collection table ... annotation is specified, a single join column is assumed and the default values apply. Example 1 ... ", joinColumns=@JoinColumn(name="STORE")) @Column(name="COPIES_IN_STOCK") @MapKeyJoinColumn(name |
