--- title: Drop, move, and rename columns --- Queries often call for dropping, moving, or renaming columns in a table. This guide covers doing so programmatically. The following methods drop columns from a table: - [`dropColumns`](../reference/table-operations/select/drop-columns.md) - [`select`](../reference/table-operations/select/select.md) - [`view`](../reference/table-operations/select/view.md) The following methods move columns in a table: - [`moveColumns`](../reference/table-operations/select/move-columns.md) - [`moveColumnsDown`](../reference/table-operations/select/move-columns-down.md) - [`moveColumnsUp`](../reference/table-operations/select/move-columns-up.md) - [`select`](../reference/table-operations/select/select.md) - [`view`](../reference/table-operations/select/view.md) The following methods rename columns in a table: - [`renameColumns`](../reference/table-operations/select/rename-columns.md) - [`select`](../reference/table-operations/select/select.md) - [`view`](../reference/table-operations/select/view.md) The examples in this guide will use the following table: ```groovy test-set=1 source = newTable( stringCol("Name", "Andy", "Claire", "Jane", "Steven"), intCol("StudentID", 1, 2, 3, 4), intCol("TestGrade", 85, 95, 88, 72), intCol("HomeworkGrade", 85, 95, 90, 95), doubleCol("GPA", 3.0, 4.0, 3.7, 2.8), ) ``` ## Remove columns from a table ### `dropColumns` [`dropColumns`](../reference/table-operations/select/drop-columns.md) removes one or more columns from a table based on the column names it's given. ```groovy test-set=1 order=resultDropOneCol,resultDropTwoCols resultDropOneCol = source.dropColumns("GPA") resultDropTwoCols = source.dropColumns("TestGrade", "HomeworkGrade") ``` ### `view` [`view`](../reference/table-operations/select/view.md) removes any columns not given as input that are present in the source table. If [`view`](../reference/table-operations/select/view.md) is not given any input, it returns a table the same as the source table but with all formula columns. > [!IMPORTANT] > Formula columns initially store only the formulas used to create columnar data. Values are calculated on the fly as needed. The following code block uses [`view`](../reference/table-operations/select/view.md) to remove the `StudentID` column from the `source` table. ```groovy test-set=1 resultNoStudentId = source.view("Name", "TestGrade", "HomeworkGrade", "GPA") ``` ### `select` [`select`](../reference/table-operations/select/select.md) is similar to [`view`](../reference/table-operations/select/view.md) in that it removes any columns not given as input that are present in the source table. However, unlike [`view`](../reference/table-operations/select/view.md),[`select`](../reference/table-operations/select/select.md) creates in-memory columns. > [!IMPORTANT] > In-memory columns store _all_ of their data in memory. This includes columns of any type, such as formula or memoized columns. Be careful when using [`select`](../reference/table-operations/select/select.md) with large tables, as it can consume a lot of memory. The following code block uses [`select`](../reference/table-operations/select/select.md) to remove the `Name` column from the `source` table. ```groovy test-set=1 resultNoName = source.select("StudentID", "TestGrade", "HomeworkGrade", "GPA") ``` ## Move columns in a table ### `moveColumns` [`moveColumns`](../reference/table-operations/select/move-columns.md) moves one or more columns to a specified column index in the resulting table. The following code block uses [`moveColumns`](../reference/table-operations/select/move-columns.md) twice: once to move a single column further right, and once to move multiple columns further right. ```groovy test-set=1 order=resultMoveOne,resultMoveTwo resultMoveOne = source.moveColumns(3, "StudentID") resultMoveTwo = source.moveColumns(2, "Name", "StudentID") ``` ### `moveColumnsUp` [`moveColumnsUp`](../reference/table-operations/select/move-columns-up.md) moves one or more columns to the zeroth column index (the left) in the resulting table. The following example moves `StudentID` to the leftmost position in the table. ```groovy test-set=1 resultStudentIdFirst = source.moveColumnsUp("StudentID") ``` ### `moveColumnsDown` [`moveColumnsDown`](../reference/table-operations/select/move-columns-down.md) moves one or more columns to the last column index (the right) in the resulting table. The following example moves `TestGrade` and `HomeworkGrade` to the rightmost position in the table. ```groovy test-set=1 resultGradesLast = source.moveColumnsDown("TestGrade", "HomeworkGrade") ``` ## Rename columns in a table ### `renameColumns` [`renameColumns`](../reference/table-operations/select/rename-columns.md) renames one or more columns in a table. Renaming a column follows the syntax `NewColumnName = OldColumnName`. > [!IMPORTANT] > If the new column name conflicts with an existing column name in the table, the existing column will be silently replaced. The following example renames `StudentID` to `ID` and `GPA` to `GradePointAverage`. ```groovy test-set=1 resultRenamed = source.renameColumns("ID = StudentID", "GradePointAverage = GPA") ``` ### `view` and `select` Renaming columns with [`view`](../reference/table-operations/select/view.md) and [`select`](../reference/table-operations/select/select.md) follows the same syntax as [`renameColumns`](../reference/table-operations/select/rename-columns.md) (`NewColumnName = OldColumnName`). As we saw previously when [removing columns](#remove-columns-from-a-table), [`select`](../reference/table-operations/select/select.md) and [`view`](../reference/table-operations/select/view.md) take a list of column names as input. The following example uses both [`select`](../reference/table-operations/select/select.md) and [`view`](../reference/table-operations/select/view.md) to rename the `Name` column to `StudentName`. > [!IMPORTANT] > [`select`](../reference/table-operations/select/select.md) creates in-memory columns. Be careful when using [`select`](../reference/table-operations/select/select.md) with large tables, as it can consume a lot of memory. ```groovy test-set=1 order=resultSelectRenamed,resultViewRenamed resultSelectRenamed = source.select( "StudentName = Name", "StudentID", "TestGrade", "HomeworkGrade", "GPA" ) resultViewRenamed = source.view( "StudentName = Name", "StudentID", "TestGrade", "HomeworkGrade", "GPA" ) ``` ## Related documentation - [Create a new table](./new-and-empty-table.md#newtable) - [Selecting and creating columns](./use-select-view-update.md) - [`dropColumns`](../reference/table-operations/select/drop-columns.md) - [`moveColumns`](../reference/table-operations/select/move-columns.md) - [`moveColumns_down`](../reference/table-operations/select/move-columns-down.md) - [`moveColumns_up`](../reference/table-operations/select/move-columns-up.md) - [`renameColumns`](../reference/table-operations/select/rename-columns.md) - [`select`](../reference/table-operations/select/select.md) - [`view`](../reference/table-operations/select/view.md)