How to turn character types into numeric values ​​in sql

In SQL, the methods for converting character data into numerical values ​​are: 1. The CAST function casts the data type; 2. The CONVERT function is similar to the CAST function; 3. The TO_NUMBER function is specifically used for character to numbers (Oracle); 4. The NUMERIC function allows specifying precision and decimal places (SQL Server).

How to convert character data to numerical values

In SQL, converting character data into numeric values ​​can be done by:

1. CAST function

The CAST function can cast one data type to another. The syntax is as follows:

 <code class="sql">CAST(expression AS data_type)</code>

For example, convert the character column "salary" to a number:

 <code class="sql">SELECT CAST(salary AS DECIMAL) FROM employees;</code>

2. CONVERT function

The CONVERT function is similar to the CAST function and is used to convert one data type to another. The syntax is as follows:

 <code class="sql">CONVERT(data_type, expression)</code>

For example, convert the character column "id" to an integer:

 <code class="sql">SELECT CONVERT(INT, id) FROM customers;</code>

3. TO_NUMBER function (Oracle)

The TO_NUMBER function is specifically used to convert character data into numbers. The syntax is as follows:

 <code class="sql">TO_NUMBER(expression)</code>

For example, convert the character column "qty" to a floating point number:

 <code class="sql">SELECT TO_NUMBER(qty) FROM orders;</code>

4. NUMERIC Function (SQL Server)

The NUMERIC function can convert character data into numbers and allow for specified precision and decimal places. The syntax is as follows:

 <code class="sql">NUMERIC(precision, scale, expression)</code>

For example, convert the character column "price" to a number with 10-bit precision and 2-bit decimals:

 <code class="sql">SELECT NUMERIC(10, 2, price) FROM products;</code>

Notice:

• When using these functions, make sure character data can be legally converted to numeric values. Otherwise, the function will return an error.
• After conversion, the accuracy and decimal places of the data may be different from the original character data.

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