select PaymentAmount, MonthID from

CustomerTable, MonthlyPaymentTable

where:

CustomerTable.

CustomerId=MonthlyPaymentTable.CustomerId

Figure 3 shows that it’s possible to represent hierarchical data in relational tables. This opens up numerous possibilities for data sources that have embedded array structures.

Importance of SQL Data Access

When the Tower of Babel builders lost their common language, they were scattered throughout the earth. Before the creation of relational databases, data access was in a Babel state. Databases and indexed files were proprietary. However, with the standardization of SQL in 1986, many relational databases recognized that supporting this standard offered distinct advantages. SQL offered easy access to data with few statements. For instance, to access an order record, the following query could be submitted:

Select order_id, customer_id, order_amt from

orders where order_id='111222'

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