cross join to get all possible user-date combinations SELECT cast(generate_series(min(action_date), max(action_date), create vector containing all dates in date range Then used in the SELECT verification to prevent the output from wrapping.WITH users (user_id, action_date, action) Query from wrapping past the edge of the terminal. The address column is set with two stringĬonstants that are attached through the || operator in order to prevent the || text concatenation operator, and the substr()įunction, in practical usage. Verifies that the desired information was updated.Įxample 4-55 also demonstrates the use of the The SELECT statement following the update Notice that severalĮscape the input apostrophes. The UPDATE statement in Example 4-55 shows both the name andĪddress columns assigned through string constants. O'Reilly & Associates | O'Reilly & Associates, Inc. 'īooktown-# || '101 Morris St, Sebastopol, CA 95472'īooktown=# SELECT name, substr(address, 1, 40) || '.' AS short_address Finally, this new profit margin is multiplied by the base costįrom the cost column, resulting in the new price with which the retail column should be updated.īooktown-# SET name = 'O\'Reilly & Associates',īooktown-# address = 'O\'Reilly & Associates, Inc. This is necessary due to the result of the division sub-expression returning a value of type The 0.1::numeric syntaxĮxplicitly casts the floating point constant to a value of type numeric. Operator and a floatingpoint constant of 0.1. Margin of the book, which is then incremented by one tenth with the + The (retail / cost) sub-expression determines the current profit TheĮxpression itself has several components, separated by parentheses to enforce order of It uses a mathematical expression to raise the retail price of each stocked book. This isĮxample 4-54 demonstrates using an UPDATE statement on the stock tableâs retailĬolumn. Thus, each row is updated to a valueĭetermined dynamically by the interpreted expressionâs value for each row. It is re-evaluated just before updating each row. When an expression is specified in the SET clause, Useful when updating columns with an expression rather Will modify each of the values within the entire specified column. If the WHERE clause is omitted, an UPDATE statement The WHERE clause constrains any modifications to rows that match the criteria described It instructs PostgreSQL to update the value in the stock tableâs retail column with the floating-point constant value of 29.95. May be used to qualify sources in the FROM clause, as you would in aĮxample 4-53 demonstrates a simple UPDATE statement. The WHERE clause describes the condition upon which a row in table will be updated. Table columns from other data sets to update a columnâs value. The FROM clause is a non-standard PostgreSQL extension that allows (which may not be aliased, or dot-notated), and where expression describes the new value to be inserted into the This expression isĪlways of the form column = expression, whereĬolumn is the name of the column to be updated The required SET clause is followed by an update expression for eachĬolumn name that needs to have its values modified, separated by commas. The ONLY keyword may be used to indicate that only the table
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