Performance Schema Summary Tables The  events_statements_summary_by_digest  table has these additional summary columns: Timestamps indicating when statements with the given digest value were first seen and most recently seen. For access to the histogram data, use the tables described in Section 27.12.20.4, “Statement Histogram Summary Tables” . The  events_statements_summary_by_digest  table contains the following columns. These are neither grouping nor summary columns; they support statement sampling: A sample SQL statement that produces the digest value in the row. This column enables applications to access, for a given digest value, a statement actually seen by the server that produces that digest. One use for this might be to run  EXPLAIN  on the statement to examine the execution plan for a representative statement associated with a frequently occurring digest. When the  QUERY_SAMPLE_TEXT  column is assigned a value, the  QUERY_SAMPLE_SEEN  and QUERY_SAMPLE_TIMER_WAIT  columns are assigned values as well. The maximum space available for statement display is 1024 bytes by default. To change this value, set the  performance_schema_max_sql_text_length  system variable at server startup. (Changing this value affects columns in other Performance Schema tables as well. See Section 27.10, “Performance Schema Statement Digests and Sampling” .) For information about statement sampling, see Section 27.10, “Performance Schema Statement Digests and Sampling” . A timestamp indicating when the statement in the  QUERY_SAMPLE_TEXT  column was seen. The wait time for the sample statement in the  QUERY_SAMPLE_TEXT  column. The  events_statements_summary_by_program  table has these additional summary columns: Statistics about nested statements invoked during stored program execution. The  prepared_statements_instances  table has these additional summary columns: 5056 • COUNT_EXECUTE ,  SUM_TIMER_EXECUTE ,  MIN_TIMER_EXECUTE ,  AVG_TIMER_EXECUTE , MAX_TIMER_EXECUTE • COUNT_STATEMENTS ,  SUM_STATEMENTS_WAIT ,  MIN_STATEMENTS_WAIT ,  AVG_STATEMENTS_WAIT , MAX_STATEMENTS_WAIT • QUERY_SAMPLE_TIMER_WAIT • QUERY_SAMPLE_SEEN • QUERY_SAMPLE_TEXT • QUANTILE_999 : Similar to  QUANTILE_95 , but for the 99.9th percentile. • QUANTILE_99 : Similar to  QUANTILE_95 , but for the 99th percentile. • QUANTILE_95 : The 95th percentile of the statement latency, in picoseconds. This percentile is a high estimate, computed from the histogram data collected. In other words, for a given digest, 95% of the statements measured have a latency lower than  QUANTILE_95 . • FIRST_SEEN ,  LAST_SEEN