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<title>ALTER TABLE Command</title>
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<span style="font-family:Helvetica,Arial; font-size:12pt; color:#000000"><b>ALTER TABLE Command
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ALTER TABLE allows you to change the structure of an existing table.
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<b>Syntax
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</b></span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">ALTER TABLE [ MEMORY ] <i>table_name</i> <i>alter_specification</i></span><span style="font-family:Times New Roman; font-size:12pt; color:#000000">
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</span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">where <i>alter_specification</i> is:
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<table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="28"></td><td><span style="font-family:Helvetica,Arial; font-size:4pt; color:#000000"></span></span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">ADD ( [ [ IF NOT EXISTS ] <i>column_definition </i>] [, ... ] [ <i>index_definition</i> ] [, ... ] )
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</span></td></tr></table><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="28"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"></span></td></tr></table><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">| MODIFY ( [ <i>column_definition </i>] [, ... ] )
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</span></span></td></tr></table><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">| DROP ( [ <i>column_name </i>] [, ... ] )
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</span></td></tr></table><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">| RENAME [ COLUMN ] <i>old_column_name</i> [ TO ] <i>new_column_name</i>
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</span></td></tr></table><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">| RENAME [ TABLE ] [ TO ] <i>new_table_name</i>
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<b>Description
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</span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">ALTER TABLE allows you to change the structure of an existing table. For example, you can add or delete columns, create indexes, change the type of existing columns, or rename columns or the table itself.
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</span><span style="font-family:Times New Roman; font-size:12pt; color:#000000"> </span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">
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MEMORY
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<table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">If MEMORY keyword is specified before the <i>table_name</i> then an in-memory table will be altered, not a disk one.
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</span></span></td></tr></table><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"></span></td></tr></table><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"></span><span style="font-family:Helvetica,Arial; font-size:4pt; color:#000000">
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</span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"><i>table_name</i>
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<table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">The name of the table to be altered.
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</span></span></td></tr></table><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"></span></td></tr></table><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"></span><span style="font-family:Helvetica,Arial; font-size:4pt; color:#000000">
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</span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">ADD<i> </i>
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<table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">Adds the new column(s) and index(es) using the same syntax as <a href=createtablestatement.htm>CREATE TABLE</a>.</span></span><span style="font-family:Times New Roman; font-size:12pt; color:#000000">
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</span></td></tr></table><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Times New Roman; font-size:12pt; color:#000000"></span></td></tr></table><span style="font-family:Times New Roman; font-size:12pt; color:#000000"></span><span style="font-family:Helvetica,Arial; font-size:4pt; color:#000000">
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</span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">IF NOT EXISTS
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<table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">If this keyword is specified, the coulmn will be created, only if there is no existing column with the same name. If this keyword is not specified and the column already exists, an exception will be raised.
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</span></span></td></tr></table><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"></span></td></tr></table><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"></span><span style="font-family:Helvetica,Arial; font-size:4pt; color:#000000">
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</span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">MODIFY<i> </i>
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<table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">Changes the column(s) settings such as data type, size, default value, etc.. </span></span><span style="font-family:Times New Roman; font-size:12pt; color:#000000">
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</span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">DROP<i> </i>
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<table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">Deletes the specified column(s).</span></span><span style="font-family:Times New Roman; font-size:12pt; color:#000000">
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</span></td></tr></table><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Times New Roman; font-size:12pt; color:#000000"></span></td></tr></table><span style="font-family:Times New Roman; font-size:12pt; color:#000000"></span><span style="font-family:Helvetica,Arial; font-size:4pt; color:#000000">
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</span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">RENAME COLUMN<i> </i>
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<table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">Changes a name of a column to the <i>new_column_name</i> value.</span></span><span style="font-family:Times New Roman; font-size:12pt; color:#000000">
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</span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">RENAME TABLE<i> </i>
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<table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">Changes a name of a table to the <i>new_table_name</i> value.
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</span></span></td></tr></table><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"></span></td></tr></table><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"></span><span style="font-family:Times New Roman; font-size:12pt; color:#000000">
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</span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000"><b>Example:
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</b><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr valign="top"><td width="14"></td><td><span style="font-family:Helvetica,Arial; font-size:4pt; color:#000000"></span></span><span style="font-family:Helvetica,Arial; font-size:10pt; color:#000000">ALTER TABLE employee ADD (height Float);
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