Power BI

Merge Queries joins two Power Query queries side by side on matching key columns, producing a wider table. Append Queries stacks their rows, producing a taller table. Merge is a SQL-style join; Append behaves like UNION ALL.

By default the clicked point cross-highlights the page: other charts keep their full bars but shade the selected share, while tables, matrices and cards are filtered outright. Edit interactions sets each target visual to Filter, Highlight or None.

Publishing a .pbix creates two workspace items: the report (pages and visuals) and the semantic model (queries, relationships, DAX and imported data). A file that live-connects to an existing model publishes the report only.

Cardinality declares which side of the relationship holds unique key values; cross-filter direction declares which way a filter travels along it. A one-to-many relationship filters from the one side down to the many side, and by default not back.

A boolean filter argument in CALCULATE replaces any existing filter on the same column rather than intersecting with it, while leaving filters on other columns intact. Wrap it in KEEPFILTERS to intersect instead of overwrite.

Filter context is the set of filters restricting which model rows a DAX expression sees; it comes from visuals, slicers and CALCULATE. Row context is a pointer to one current row inside a calculated column or an iterator, and it does not filter anything by itself.

Query folding is Power Query translating Applied Steps into a single native query the source executes, so filtering and aggregation happen at the source. Steps M cannot translate — an index column, Table.Buffer, cross-source merges — end folding, and everything after runs locally.

The values of the fields placed in the target page's drill-through well, taken from the clicked data point. With Keep all filters on, the source visual's other filters travel too, so the detail page matches the context the reader came from.

One role filters a user-mapping table with [UserEmail] = USERPRINCIPALNAME(), which returns the signed-in user's UPN. That row set propagates through relationships to the dimensions and facts, so a single role serves every user and permissions become refreshable data.

A Power BI role holds a DAX boolean filter on one or more tables. The engine applies it to every query the assigned user runs and propagates it along relationships, so excluded rows never reach visuals, totals or exports.

A gateway is needed whenever the Power BI Service cannot reach the source directly — anything on-premises or inside a private network. Cloud sources reachable over the public internet refresh without one. DirectQuery and live connections to on-prem sources need the standard gateway.

DIVIDE is DAX's safe division function: when the denominator is zero or blank it returns BLANK, or an alternate result you pass as the third argument. The / operator instead yields Infinity or NaN, which then leaks into the visual.

Use Desktop's View as feature to render the report under a chosen role, and for dynamic RLS also as another user by typing their UPN. After publishing, the semantic model's security page in the Power BI Service can test the report as a role.

Power BI adds a hidden blank row to the one side of a relationship when the fact table contains key values that have no match, or nulls. Those fact rows are grouped under (Blank) so the total still includes them.

SUMX multiplies quantity by price inside each row and then adds the results, so every row uses its own price. Multiplying two SUMs multiplies a total quantity by a total price, which is a number no transaction ever had.

Wrap the query's let expression in an M lambda — (p as text) as table => let … in … — or use Create Function on a query driven by parameters. Invoking it per row adds a table column you expand, and each row is a separate source call.

That single cell becomes an Error value rather than failing the query; surrounding rows load normally. A step-level failure is different — a missing or renamed column aborts the whole query. Handle cell errors explicitly with try/otherwise, Replace Errors or Remove Errors.

A Power BI bookmark saves the page's current state — filter and slicer selections, cross-highlight selection, sort order, drill level, and which visuals are shown or hidden — so a button can restore it. It stores no data; visuals re-query the model when applied.

Use a Power BI app once an audience is larger than a handful or the content is finished: it packages chosen workspace items into a stable read-only experience with its own audiences. Direct share links suit ad-hoc, one-off access and sprawl badly at scale.

Bidirectional filtering lets filters travel back up from the fact table, which can create more than one route between tables, make results depend on the path taken, slow queries, and interact badly with row-level security. Scope it per measure instead.

Use a bridge table whenever you need strong relationships, a slicer over the shared keys, or reliable totals. Power BI's many-to-many cardinality creates a limited relationship: no blank row for unmatched keys, no RELATED, and totals that can stop matching the visible rows.

DAX time-intelligence functions shift a set of dates and reapply it as a filter, which requires a dedicated date table with one row per contiguous calendar day, related to the fact table and marked as a date table. Gaps, duplicates, or filtering the fact table's own date column break the shift.

The total is not a sum of the displayed cells. Power BI evaluates the same DAX measure again in the total's filter context, with the row grouping removed, so any non-additive measure — a ratio, a distinct count, a conditional — legitimately returns something else.

Run Performance Analyzer in Power BI Desktop: it records each visual's time split into DAX query, visual display and other, so you can see which visual dominates and whether the cost is the model query or the rendering. Fix that one rather than guessing.

The security filter only travels where model relationships carry it. Look for a missing, inactive or wrongly directed relationship, a fact table joined to a different dimension copy, or a disconnected table — and confirm the user is not exempt through workspace edit rights.

Users with workspace Admin, Member or Contributor roles hold edit permission on the semantic model, and RLS is not applied to them. Roles restrict read-only consumers — Viewers and app audiences — and a read-only user assigned to no role sees no data.

Check what actually refreshed and when the source was ready. Common causes: you refreshed a different semantic model, incremental refresh touched only recent partitions, the upstream load finished after the schedule fired, or a cached dashboard tile lags the report.

Keep in Power Query only shaping that is local to one model or reachable only through a connector — folders of files, APIs, unpivoting. Shared, expensive or auditable logic belongs upstream in the warehouse; logic that must react to user filters belongs in DAX.

Separate the governed semantic model into its own workspace with tight write access and Build permission for analysts, keep team reports in their own workspaces live-connected to it, promote changes through dev/test/prod stages, and endorse the model so people find the right one.