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in operatorthe operator in tests the set membership this means equal to any member of the set may have nulls but they are ignored for illustration
between operatorthe operator between tests whether the value lies in a specified series that means greater than or equivalent to low value and less
like operatoryou use the like operator to compare the character value to a pattern the case is significant like returns the boolean value true when
is null operatorthe is null operator returns the boolean value true whenever its operand is null or false if it is not null the comparisons including
comparison operatorsthe comparison operators can compare one expression to another the outcome is always true false or null usually you use a
short-circuit evaluation when computing a logical expression the plsql uses short-circuit evaluation that is the plsql stops computing the expression
order of evaluationwhen you do not use the parentheses to specify the order of evaluation the operator precedence determine the order now compare the
plsql expressions the expressions are constructed by using the operands and operators an operand is a constant literal variable or function call
database valuesyou can use the select statement to have the oracle assign values to a variable foreach and every item in the select list there must
boolean valuesonly the values true false amp null can be assigned to a boolean variable for illustration given the declarationdeclaredone booleanthe
assignments in plsqlthe variables and constants are initialized every time a block or subprogram is enteredby default the variables are initialized
name resolutionin potentially uncertain sql statements the names of the database columns take precedence over the names of the local variables and
case sensitivitysimilar to all the identifiers the variables the names of constants and parameters are not case sensitive for illustration plsql
scopingwithin the similar scope all the declared identifiers should be unique so even if their datatypes differ the variables and parameters cannot
synonymsyou can create the synonyms to provide location transparency for the remote schema objects like tables views sequences stand-alone
naming conventionsthe similar naming conventions apply to all plsql program items and units including the variables cursors constants cursor
using aliasesthe select-list items fetched from a cursor related with the rowtype should have simple names or if they are expressions should have
aggregate assignmentthe rowtype declaration cannot include an initialization clause though there are two ways to assign values to all fields in a
using rowtypethe rowtype attribute gives a record type which represents a row in a table or view the record can store the whole row of data selected
using typethe type attribute gives the datatype of a variable or the database column in the example below the type gives the datatype of a
using not nullbesides assigning an initial value the declarations can impose the not null constraint as the example below showsacctid integer4 not
using defaultyou can use the keyword default rather than that of the assignment operator to initialize the variables for eg the declarationbloodtype
declarations in sqlyour program stores values in the variables and constants as the program executes the value of the variables can change but the
lob typesthe large object lob datatypes like bfile blob clob and nclob store the blocks of unstructured data like graphic images text video clips and
rowid and urowidinternally every database table has a rowid pseudo column that stores binary values known as rowids each rowid shows the storage