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Generating SQL

In the sections to come, we explain how to make Mass Change generate SQL statements based on the information you entered in the type, template, and definition pages. However, in order to know what information to provide, you should understand a bit about how Mass Change uses that information.

As we explained earlier, the SQL Action values in the Records and Join Fields page tell Mass Change what kind of SQL statement to generate; the Record values specify which records and fields will be used in the statement.

Insert and Select SQL actions work together. If a SQL Statement contains an Insert action, Mass Change creates an INSERT statement and uses all Select-action records for creating the associated SELECT clause. It doesn’t matter where in the sequence the Selects and Inserts occur. If more than one Insert action exists in a SQL Statement row, additional INSERT statements will be generated, all using the same SELECT clause. In short, Mass Change can create multiple SQL statements using the information from one SQL Statement row.

The name SQL Statement on the Records and Join Fields page is a little misleading because Mass Change can actually generate a number of statements from one SQL Statement row, depending on your Record and SQL Action selections.

Typically, we recommend limiting your page selections to create just one SQL statement per SQL Statement row. For example, put an Update-action record in one SQL Statement row, put a Delete-action record in another, and so on. However, in cases where Inserts share a common SELECT clause, it makes sense to put them all in one SQL Statement so you don’t have to set up the Select records over and over. If you have multiple Inserts that each require a different SELECT clause, then you must put each Insert in its own SQL Statement row.

Note: SQL Statement rows that contain Select actions with no Inserts will not generate any SQL. Select actions must be associated with at least one Insert action.

Mass Change always includes the tables MC_DEFN and MC_DEFN_owner in the FROM portion of SELECT clauses. The fields in these tables are used to control execution and to add null values for time, date, and datetime fields, if necessary. Therefore, if you specify an Insert-action record without specifying at least one Select-action record, Mass Change will still generate a SQL statement. However, it will result in added rows that are empty except for any system field defaults or MC_DEFN fields that match up.

In addition, Mass Change always ends each SELECT clause with the following WHERE clause:

WHERE MC_DEFN.MC_DEFN_ID = '<definition_ID>' 

If any other WHERE conditions are supplied—from join fields, criteria fields, or an additional Where clause—Mass Change appends them to this clause.