alter-table.html

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            <h1>SQL ALTER TABLE Statement</h1>

            <p>The <strong>ALTER TABLE</strong> statement is used to add, delete, or modify columns in an existing
                table.
                It is also used to add or drop various constraints on an existing table.</p>
            <p><strong>Note:</strong> ALTER/MODIFY COLUMN syntax is not supported in this tutorial.</p>

            <h2>ALTER TABLE - ADD Column Syntax</h2>
            <pre><code class="language-sql">ALTER TABLE table_name
ADD column_name datatype;</code></pre>

            <p>Example: Add an "email" column to the "patients" table:</p>
            <pre><code class="language-sql">ALTER TABLE patients
ADD email varchar(255);

SELECT patient_id, email FROM patients;</code></pre>

            <h2>ALTER TABLE - DROP COLUMN Syntax</h2>
            <p>To delete a column in a table:</p>
            <pre><code class="language-sql">ALTER TABLE table_name
DROP COLUMN column_name;</code></pre>

            <p>Example: Delete the "last_name" column from the "patients" table:</p>
            <pre><code class="language-sql">ALTER TABLE patients
DROP COLUMN last_name;

SELECT * FROM patients;</code></pre>

            <h2>ALTER TABLE - ALTER/MODIFY COLUMN Syntax</h2>
            <p>To change the data type of a column in a table:</p>
            <pre><code class="language-sql">-- SQL Server / MS Access
ALTER TABLE table_name
ALTER COLUMN column_name datatype;

-- MySQL / Oracle (prior to 10G)
ALTER TABLE table_name
MODIFY COLUMN column_name datatype;

-- Oracle 10G and later
ALTER TABLE table_name
MODIFY column_name datatype;</code></pre>
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