github.com/mithrandie/csvq@v1.18.1/docs/_posts/2006-01-02-alter-table-query.md (about)

     1  ---
     2  layout: default
     3  title: Alter Table Query - Reference Manual - csvq
     4  category: reference
     5  ---
     6  
     7  # Alter Table Query
     8  
     9  Alter Table query is used to modify data structure.
    10  
    11  * [ADD COLUMNS](#add-columns)
    12  * [DROP COLUMNS](#drop-columns)
    13  * [RENAME COLUMN](#rename-column)
    14  * [SET ATTRIBUTE](#set-attribute)
    15  
    16  ## Add Columns
    17  {: #add-columns}
    18  
    19  ```sql
    20  ALTER TABLE table_name
    21    ADD column_name [DEFAULT value]
    22    [FIRST|LAST|AFTER column|BEFORE column]
    23  
    24  ALTER TABLE table_name
    25    ADD (column_name [DEFAULT value] [, column_name [DEFAULT value] ...])
    26    [FIRST|LAST|AFTER column|BEFORE column]
    27  ```
    28  
    29  _table_name_
    30  : [identifier]({{ '/reference/statement.html#parsing' | relative_url }}) or [Table Object]({{ '/reference/select-query.html#from_clause' | relative_url }})
    31  
    32  _column_name_
    33  : [identifier]({{ '/reference/statement.html#parsing' | relative_url }})
    34  
    35  _value_
    36  : [value]({{ '/reference/value.html' | relative_url }})
    37    
    38    If default value is not specified, new fields are set null.
    39  
    40  _column_
    41  : [field reference]({{ '/reference/value.html#field_reference' | relative_url }})
    42  
    43  _LAST_ is the default position.
    44  
    45  
    46  ## Drop Columns
    47  {: #drop-columns}
    48  
    49  ```sql
    50  ALTER TABLE table_name DROP column
    51  ALTER TABLE table_name DROP (column [, column ...])
    52  ```
    53  
    54  _table_name_
    55  : [identifier]({{ '/reference/statement.html#parsing' | relative_url }}) or [Table Object]({{ '/reference/select-query.html#from_clause' | relative_url }})
    56  
    57  _column_
    58  : [field reference]({{ '/reference/value.html#field_reference' | relative_url }})
    59  
    60  ## Rename Column
    61  {: #rename-column}
    62  
    63  ```sql
    64  ALTER TABLE table_name RENAME old_column_name TO new_column_name
    65  ```
    66  
    67  _table_name_
    68  : [identifier]({{ '/reference/statement.html#parsing' | relative_url }}) or [Table Object]({{ '/reference/select-query.html#from_clause' | relative_url }})
    69  
    70  _old_column_name_
    71  : [field reference]({{ '/reference/value.html#field_reference' | relative_url }})
    72  
    73  _new_column_name_
    74  : [identifier]({{ '/reference/statement.html#parsing' | relative_url }})
    75  
    76  ## Set Attribute
    77  {: #set-attribute}
    78  
    79  Set file attributes. 
    80  File attributes is used to create or update files by the results of queries.
    81  
    82  Changes to the file attributes are retained until the end of the transaction.
    83  
    84  
    85  ```sql
    86  ALTER TABLE table_name SET attribute TO value
    87  ```
    88  
    89  _table_name_
    90  : [identifier]({{ '/reference/statement.html#parsing' | relative_url }}) or [Table Object]({{ '/reference/select-query.html#from_clause' | relative_url }})
    91  
    92  _attribute_
    93  : [identifier]({{ '/reference/statement.html#parsing' | relative_url }})
    94  
    95    | name | type | description |
    96    | :- | :- | :- |
    97    | FORMAT              | string  | Format |
    98    | DELIMITER           | string  | Field delimiter for CSV |
    99    | DELIMITER_POSITIONS | string  | Delimiter positions for Fixed-Length Format |
   100    | JSON_ESCAPE         | string  | JSON escape type |
   101    | ENCODING            | string  | File Encoding |
   102    | LINE_BREAK          | string  | Line Break |
   103    | HEADER              | boolean | Write header line in the file |
   104    | ENCLOSE_ALL         | boolean | Enclose all string values in CSV |
   105    | PRETTY_PRINT        | boolean | Make JSON output easier to read |
   106  
   107  _value_
   108  : [value]({{ '/reference/value.html' | relative_url }}) or [identifier]({{ '/reference/statement.html#parsing' | relative_url }})