This approach doesn't require the same number of values as attributes, and it also allows arbitrary ordering of the attributes. The number of values inserted is the same as the number of attributes in the table and an error is generated if the number of values doesn't match the number of attributes. We describe the latter three statements in this section. For example, a popular variation is to insert data from another table using a query or to insert data from a formatted text file. You can update more than one attribute in a statement. Consider a simple example: As we show you later in Chapter 8 , this also helps avoid concurrency problems and, therefore, the need for locking when several users are using the same database. For example, if there are already 10 rows in the names table with id values of 1 to 10, inserting a row with NULL as the id or not providing an id and invoking the default behavior creates a row with an id value of
Data can also be inserted using a second approach. The disadvantage is that it's a proprietary MySQL feature. To check an identifier value, the function should be called immediately after inserting the new row. The second value 'Williams' is inserted into the second attribute surname, 'Lucy' into firstname, and so on. As we show you later in Chapter 8 , this also helps avoid concurrency problems and, therefore, the need for locking when several users are using the same database. These two approaches and other variants are discussed in Chapter This can save you lots of typing when a row has many attributes but is sparsely populated with values. We show both approaches by inserting the same data for a new customer, Lucy Williams. There are other ways to insert data in addition to those discussed here. For example, to create a partial customer row, you could use: Consider an example of the first approach using the customer table: Numeric values can also be enclosed in quotes but they aren't mandatory. Inserting a row can follow two different approaches. You can update more than one attribute in a statement. The number of values inserted is the same as the number of attributes in the table and an error is generated if the number of values doesn't match the number of attributes. We describe the latter three statements in this section. This approach doesn't require the same number of values as attributes, and it also allows arbitrary ordering of the attributes. Consider a second example: Consider an example that uses the latter approach and inserts the details for two customers: For example, consider the string "Steve O'Dwyer". Likewise, strings containing double quotation marks can be enclosed in single quotation marks. Consider a simple example: For example, the following deletes all data in the customer table but doesn't remove the table: If MySQL finds that a value doesn't need to be changed because it's already set to the value you want to change it to , it isn't updated and isn't included in the count that's returned. If a string contains single quotation marks, the string can be enclosed in double quotation marks. For example, you can create an incomplete customer row with: For the previous example, you can check which id was created with the statement:
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