> ## Knowledge Base Index > Fetch the complete knowledge base index at: https://help.lido.app/sitemap.xml > Use this file to discover available pages before exploring further. > Pure-Markdown content can be obtained by appending a '.md' suffix to the content URLs listed in the sitemap (without the trailing slash). # Tables: how columns work A Lido table is a named, structured dataset inside your spreadsheet. Every column has a specific role — computed, linked, plain, or sourced from external data — and that role determines how values get into the cells. This article explains each column type and when to use it. --- ## Why tables matter A regular spreadsheet range is just cells. A Lido table is a *named* dataset whose columns have *behavior*. Tables let you: - Reference data by name (`Orders[@Price]`) instead of by cell address. - Pull rows from external sources that refresh automatically. - Combine computed fields, manually-edited fields, and source-fed fields in the same dataset. - Apply transformations (filter, sort, group) without breaking downstream formulas. --- ## The four column types | Column type | What it does | When to use | | --- | --- | --- | | **Source** | Values come from an external source (CRM, database, API, file). Refresh automatically. | The data lives somewhere else and you want it kept in sync. | | **Computed** | A formula runs once per row and produces the value. Same formula for every row. | Calculated fields like Total = Price × Quantity. | | **Linked** | Each row stores its own independent value, keyed by an ID column. Different formula or value per row. | Per-row notes, manual overrides, row-specific logic. | | **Plain** | Empty column for manual data entry. No formula. | Status fields, comments, anything you'll type by hand. | A single table can mix all four. A Products table might pull rows from a CRM (source), calculate Revenue (computed), have an Override Price (linked), and a Notes column (plain). --- ## Computed columns A computed column applies the same formula to every row. Type a formula in a cell immediately to the right of the table and Lido turns it into a computed column. ``` =Orders[@Price] * Orders[@Quantity] ``` Lido evaluates this for every row, resolving `[@Price]` and `[@Quantity]` to the values in that row. You can also use template strings for simple text construction: ``` {First Name} {Last Name} ``` **Restriction:** the formula inside a computed column cannot create another column. Don't nest `COMPUTEDCOLUMN`, `LINKEDCOLUMN`, `MAKETABLE`, `RANGETABLE`, or `PLAINCOLUMN` inside a computed column. Under the hood, Lido stores it as: `=COMPUTEDCOLUMN(formula, table_name, column_name)`. --- ## Linked columns A linked column stores a separate value or formula for each row, keyed by an ID column. Use it when: - Some rows have manual overrides and others use a default formula. - Each row needs row-specific behavior (different notes, different rules). - You want manual edits to follow the row even when the table is filtered or sorted. The ID column must have unique values. Duplicates cause an error. If a row's ID changes, its linked value follows the new ID — meaning you can rename a record without losing its custom data. Under the hood: `=LINKEDCOLUMN(table_name, id_column_name, column_name, lc_id)`. Lido auto-generates the `lc_id`. --- ## Plain columns The simplest column type. No formula. Users type values directly. Use plain columns for: - Status fields ("Approved", "Rejected", "Pending") - Notes and comments - Manually-entered fields that don't have a calculation behind them Under the hood: `=PLAINCOLUMN(table_name, column_name)`. --- ## Source columns A source column's values come from an external source — a CRM, database, generic API, file, or other connection. Lido refreshes the values on a schedule (or manually, on demand). Source columns are created when you set up an external data source via **File → Connect real-time data**. You don't add source columns one at a time; the connection wizard creates the table and columns together. See: **Connect a real-time data source** for setup. --- ## Adding columns to an existing table To add a new column, start typing in any empty cell immediately to the right of the table. Lido detects you're extending the table and prompts you to pick the column type: - Type a formula → computed column - Type a value → plain column - Lido may suggest a linked column if the table has a unique ID column and the value looks per-row You can rename, reorder, and delete columns from the column header menu. --- ## Referencing tables in formulas Three syntaxes: | Syntax | Returns | Example | | --- | --- | --- | | `TableName[@ColumnName]` | The value in that column **for the current row** | `Orders[@Price]` | | `TableName[ColumnName]` | The **entire column** as an array | `SUM(Orders[Revenue])` | | `TableName[#All]` | The **entire table** (all columns, all rows) | `FILTER(Orders[#All], Orders[@Status]="Pending")` | The `@` prefix is the most common — it's used inside computed columns and in formulas next to a table. --- ## Worked example: an orders table Build a table named `Orders` from a CSV import. Then add columns: - `Subtotal` — computed: `=Orders[@Price] * Orders[@Quantity]` - `Tax` — computed: `=Orders[@Subtotal] * Orders[@Tax Rate]` - `Total` — computed: `=Orders[@Subtotal] + Orders[@Tax]` - `Status` — plain (typed manually) - `Customer Notes` — linked (different per row, follows the Order ID) Now reference the table elsewhere: ``` =SUM(Orders[Total]) =COUNTIF(Orders[Status], "Shipped") =FILTER(Orders[#All], Orders[@Status]="Pending") ``` --- ## Common mistakes - **Adding a computed column with a formula that creates another column.** Don't nest `COMPUTEDCOLUMN`, `LINKEDCOLUMN`, etc. inside a computed column. The result is unpredictable. - **Using a non-unique ID column with linked columns.** Each ID must be unique or Lido raises an error. - **Editing source column values manually.** They'll be overwritten on the next refresh. Use a separate plain or linked column for manual notes. - **Mixing up `[@Column]` and `[Column]`.** `[@Column]` returns one value (current row); `[Column]` returns an array (the whole column). --- ## Related articles - Concepts: spreadsheet vs. workflow vs. API - Actions: how spreadsheet automation works - AI columns and formulas - Expressions and the formula bar - Connect a real-time data source