SELECT

The SELECT statement reads rows from one or more tables or views. It never changes data, so it is the safest SQL to practice with.

SELECT syntax

• Basic shape: SELECT columns FROM table WHERE condition.
• SELECT * reads all columns. In programs, name the columns instead - it is faster and safer.
• Columns can come from the table, from host variables, from constants, or from calculations like SALARY + BONUS.
• Use AS to name a calculated column, for example SELECT SALARY + BONUS AS INCOME.

INTO and FROM clauses

• INTO puts the result into COBOL host variables. The number and types must match the select list.
• A single-row SELECT ... INTO needs exactly one matching row. Zero rows gives +100, more than one gives -811.
• FROM names the table or view. A typical name has two parts: creator.table, for example MM01.CUSTOMER.

WHERE clause

• WHERE keeps only the rows that satisfy the condition. Without WHERE, every row is returned.
• Comparison operators: = < > <> <= >=.
• Values can be literals ('CA'), host variables (:STATE), or expressions.

Example

• Reading one customer row into host variables:-