Column

java.lang.Object
- CompareTerm
- - Column

```
public class Column
extends CompareTerm
```
A class that represents a column in a table.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`CHAR` A column of type CHAR
`static int`	`INTEGER` A column of type INTEGER
`static int`	`MAX_WIDTH_INTEGER` The print width of an INTEGER column.
`static int`	`MAX_WIDTH_REAL` The print width of a REAL column.
`static int`	`REAL` A column of type REAL
`static int`	`VARCHAR` A column of type VARCHAR

Fields inherited from class CompareTerm
STRING

Constructor Summary

Constructors
Constructor and Description
`Column(Column col)` Constructs a Column object that has the same initial field values as the specified column.
`Column(String name)` Constructs a Column object with the specified name.
`Column(String name, Table t)` Constructs a Column object with the specified name from the specified table.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`Object`	`adjustValue(Object val)` Returns an adjusted value for this column, based on its type and length.
`void`	`applyOpts(ColumnOptions opts)` Applies the specified column options to this column.
`int`	`getIndex()` Returns the index of the column in the table to which it belongs.
`int`	`getLength()` Returns the length of the column -- i.e., the number of bytes used to represent its values.
`String`	`getName()` Returns the name of the column.
`Table`	`getTable()` Returns the table to which this column belongs.
`TableIterator`	`getTableIterator()` Returns the table iterator used to obtain values of this column IMPORTANT: if you invoke this method on a Column from a Table object's array of column information, it will return null.
`int`	`getType()` Returns the type of the column
`Object`	`getUpdateVal()` Returns the update value associated with this column -- i.e., the value it should be assigned by an update command.
`Object`	`getValue()` Returns the current value of this column, based on the row on which the corresponding table iterator is currently positioned.
`boolean`	`isNotNull()` Returns a boolean value indicating whether this column is prevented from taking on null values.
`boolean`	`isPrimaryKey()` Returns a boolean value indicating whether this column is the primary key of its table
`boolean`	`nameMatches(Column other, Table otherTable)` Determines if the column represented by the called object has the same name as the column represented by the two parameters.
`int`	`printWidth()` Returns the maximum print width for values from this column.
`void`	`resetUpdateVal()` Removes any update value associated with this column, which means that an update command will not try to update it unless a new update value is specified using `setUpdateVal`.
`void`	`setIndex(int i)` Sets the index of this column -- i.e., its index in the table to which it belongs.
`void`	`setLength(int length)` Sets the length of this column.
`void`	`setLength(Integer length)` Sets the length of this column -- i.e., the number of bytes used to represent its values.
`void`	`setTableIterator(TableIterator iter)` Sets the table iterator used to obtain the values of this column.
`void`	`setType(int type)` Sets the type of this column -- which must be one of the constants specified in this class (INTEGER, REAL, CHAR, or VARCHAR).
`void`	`setUpdateVal(Object val)` Sets the update value associated with this column, which means that any update commands will try to update it until the update value is removed using `resetUpdateVal`.
`boolean`	`shouldUpdate()` Determines whether this column should be updated by an update command -- i.e., if it has an up-to-date update value.
`String`	`toString()`
`void`	`useColInfo(Column other)` Gives the column specified by the called object the same metadata (type, length, etc.) as the specified other column.

Methods inherited from class CompareTerm
getValType, setValType

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - INTEGER
```
public static final int INTEGER
```
    A column of type INTEGER
    
    See Also:
    
    Constant Field Values
  - REAL
```
public static final int REAL
```
    A column of type REAL
    
    See Also:
    
    Constant Field Values
  - CHAR
```
public static final int CHAR
```
    A column of type CHAR
    
    See Also:
    
    Constant Field Values
  - VARCHAR
```
public static final int VARCHAR
```
    A column of type VARCHAR
    
    See Also:
    
    Constant Field Values
  - MAX_WIDTH_INTEGER
```
public static final int MAX_WIDTH_INTEGER
```
    The print width of an INTEGER column.
    
    See Also:
    
    Constant Field Values
  - MAX_WIDTH_REAL
```
public static final int MAX_WIDTH_REAL
```
    The print width of a REAL column.
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - Column
```
public Column(String name)
```
    Constructs a Column object with the specified name.
    
    Parameters:
    
    name - the name of the column
  - Column
```
public Column(String name,
              Table t)
```
    Constructs a Column object with the specified name from the specified table.
    
    Parameters:
    
    name - the name of the column
    
    t - the table to which the column belongs
  - Column
```
public Column(Column col)
```
    Constructs a Column object that has the same initial field values as the specified column. Creating a "copy" in this way allows us to have a column appear more than once in a cross product, if we are crossing a table with itself.
    
    Parameters:
    
    col - the column we want to copy
- Method Detail
  - nameMatches
```
public boolean nameMatches(Column other,
                           Table otherTable)
```
    Determines if the column represented by the called object has the same name as the column represented by the two parameters. Note that we need to specify the other table, because aliases may not be reflected in the Table object associated with the Column object.
    
    Parameters:
    
    other - the other column whose name we are comparing against
    
    otherTable - the other column's table
    
    Returns:
    
    true if the names match, and false otherwise
  - adjustValue
```
public Object adjustValue(Object val)
```
    Returns an adjusted value for this column, based on its type and length. This method performs any necessary type convertions and length adjustments to ensure that the value is valid for this column, and it will throw an IllegalArgumentException if the value cannot be converted (e.g., if a string is specified for an integer column).
    
    Parameters:
    
    val - the unadjusted value
    
    Returns:
    
    the adjusted value
    
    Throws:
    
    IllegalArgumentException - if the specified value cannot be converted to a valid value for this column
  - getValue
```
public Object getValue()
```
    Returns the current value of this column, based on the row on which the corresponding table iterator is currently positioned.
    
    Overrides:
    
    getValue in class CompareTerm
    
    Returns:
    
    the column's current value
  - printWidth
```
public int printWidth()
```
    Returns the maximum print width for values from this column.
    
    Returns:
    
    the print width
    
    Throws:
    
    IllegalStateException - if the column has an unknown type
  - setType
```
public void setType(int type)
```
    Sets the type of this column -- which must be one of the constants specified in this class (INTEGER, REAL, CHAR, or VARCHAR).
    
    Parameters:
    
    type - the column's type
    
    Throws:
    
    IllegalArgumentException - if an invalid type is specified
  - setLength
```
public void setLength(int length)
```
    Sets the length of this column.
    
    Parameters:
    
    length - the column's length
    
    Throws:
    
    IllegalArgumentException - if a 0 or negative length is specified
  - setLength
```
public void setLength(Integer length)
```
    Sets the length of this column -- i.e., the number of bytes used to represent its values. For VARCHAR columns, this should be the the maximum number of bytes. For all other columns, it should be the exact number of bytes.
    
    Parameters:
    
    length - the column's length
    
    Throws:
    
    IllegalArgumentException - if a 0 or negative length is specified or if the argument is null
  - applyOpts
```
public void applyOpts(ColumnOptions opts)
```
    Applies the specified column options to this column.
    
    Parameters:
    
    opts - the column options
  - setIndex
```
public void setIndex(int i)
```
    Sets the index of this column -- i.e., its index in the table to which it belongs. The leftmost column has an index of 0.
    
    Parameters:
    
    i - the index
    
    Throws:
    
    IllegalArgumentException - if a negative index is specified
  - resetUpdateVal
```
public void resetUpdateVal()
```
    Removes any update value associated with this column, which means that an update command will not try to update it unless a new update value is specified using setUpdateVal.
  - shouldUpdate
```
public boolean shouldUpdate()
```
    Determines whether this column should be updated by an update command -- i.e., if it has an up-to-date update value.
    
    Returns:
    
    true if the column should be updated, and false otherwise
  - setUpdateVal
```
public void setUpdateVal(Object val)
```
    Sets the update value associated with this column, which means that any update commands will try to update it until the update value is removed using resetUpdateVal.
    
    Parameters:
    
    val - the value the column should be assigned
  - useColInfo
```
public void useColInfo(Column other)
```
    Gives the column specified by the called object the same metadata (type, length, etc.) as the specified other column.
    
    Parameters:
    
    other - the column whose metadata we want to copy
    
    Throws:
    
    IllegalArgumentException - if a null argument is specified
  - setTableIterator
```
public void setTableIterator(TableIterator iter)
```
    Sets the table iterator used to obtain the values of this column.
    
    Parameters:
    
    iter - the table iterator
  - getName
```
public String getName()
```
    Returns the name of the column.
    
    Returns:
    
    the column's name
  - getTable
```
public Table getTable()
```
    Returns the table to which this column belongs. IMPORTANT: if you invoke this method on a column from the SELECT or WHERE clause with a name that isn't fully qualified (i.e., that doesn't include a table name), this method will return null.
    
    Returns:
    
    the table
  - getType
```
public int getType()
```
    Returns the type of the column
    
    Returns:
    
    the type (one of the constants defined in this class)
  - getLength
```
public int getLength()
```
    Returns the length of the column -- i.e., the number of bytes used to represent its values. For VARCHAR columns, this returns the the maximum number of bytes. For all other columns, it represents the exact number of bytes.
    
    Returns:
    
    the length
  - isNotNull
```
public boolean isNotNull()
```
    Returns a boolean value indicating whether this column is prevented from taking on null values.
    
    Returns:
    
    true if the column cannot take on null values, and false otherwise
  - isPrimaryKey
```
public boolean isPrimaryKey()
```
    Returns a boolean value indicating whether this column is the primary key of its table
    
    Returns:
    
    true if the column is the primary key, and false otherwise
  - getIndex
```
public int getIndex()
```
    Returns the index of the column in the table to which it belongs. The leftmost column has an index of 0.
    
    Returns:
    
    the index
  - getUpdateVal
```
public Object getUpdateVal()
```
    Returns the update value associated with this column -- i.e., the value it should be assigned by an update command. This method should not be used to determine whether a column should be updated, since this method will return null both when there is no update value and when there is an update value of null. To determine if a column should be updated, use the shouldUpdate() method.
    
    Returns:
    
    the update value
  - getTableIterator
```
public TableIterator getTableIterator()
```
    Returns the table iterator used to obtain values of this column IMPORTANT: if you invoke this method on a Column from a Table object's array of column information, it will return null. Only Column objects from the SELECT and WHERE clause have associated table iterators. These are set when the TableIterator is created.
    
    Returns:
    
    the table iterator
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class CompareTerm

Class Column

Field Summary

Fields inherited from class CompareTerm

Constructor Summary

Method Summary

Methods inherited from class CompareTerm

Methods inherited from class java.lang.Object

Field Detail

INTEGER

REAL

CHAR

VARCHAR

MAX_WIDTH_INTEGER

MAX_WIDTH_REAL

Constructor Detail

Column

Column

Column

Method Detail

nameMatches

adjustValue

getValue

printWidth

setType

setLength

setLength

applyOpts

setIndex

resetUpdateVal

shouldUpdate

setUpdateVal

useColInfo

setTableIterator

getName

getTable

getType

getLength

isNotNull

isPrimaryKey

getIndex

getUpdateVal

getTableIterator

toString