query-semi-join.md
In dbplyr: A 'dplyr' Back End for Databases

print method doesn't change unexpectedly

Code
  sql_build(semi_join(lf1, lf2 %>% filter(z == 2)))
Message
  Joining with `by = join_by(x)`
Output
  <SQL SEMI JOIN>
  By:
    x-x
  Where:
    "`df_RHS`.`z` = 2.0"
  X:
    <dbplyr_table_ident[1]>
    [1] `df`
  Y:
    <dbplyr_table_ident[1]>
    [1] `df`

generated sql doesn't change unexpectedly

Code
  semi_join(lf, lf)
Message
  Joining with `by = join_by(x, y)`
Output
  <SQL>
  SELECT `df_LHS`.*
  FROM `df` AS `df_LHS`
  WHERE EXISTS (
    SELECT 1 FROM `df` AS `df_RHS`
    WHERE (`df_LHS`.`x` = `df_RHS`.`x`) AND (`df_LHS`.`y` = `df_RHS`.`y`)
  )

Code
  anti_join(lf, lf)
Message
  Joining with `by = join_by(x, y)`
Output
  <SQL>
  SELECT `df_LHS`.*
  FROM `df` AS `df_LHS`
  WHERE NOT EXISTS (
    SELECT 1 FROM `df` AS `df_RHS`
    WHERE (`df_LHS`.`x` = `df_RHS`.`x`) AND (`df_LHS`.`y` = `df_RHS`.`y`)
  )