The following are the symbols for the relational algebra operators:

Operator | Symbol | HTML | Unicode | Description | Additional information required | Magnification |
---|---|---|---|---|---|---|

Projection | π | π | π | Select some of the columns of a bag | The columns to be selected | |

Extension | ξ | ξ | π | Add an additional column to a bag | The formula for computing the additional column | |

Selection | σ | σ | σ | Select some of the rows of a bag | The condition (predicate) for selecting rows | |

Rename | ρ | ρ | ρ | Change the name of a column | The old and new names | |

Product | × | × | ȕ | Cartesian product of two bags | +3 | |

Join | ⨝ | ⨝ | Join of two bags | The join condition | +2 | |

Left Join | ⟕ | ⟕ | Left outer join of two bags | +4 | ||

Right Join | ⟖ | ⟖ | Right outer join of two bags | +4 | ||

Full Outer Join | ⟗ | ⟗ | Full outer join of two bags | +4 | ||

Semijoin | ⋉ | ⋉ | Subquery with exists or "in" | +3 | ||

Antijoin | ▷ | ▷ | Subquery with not exists or "not in" | +1 | ||

Union | ∪ | ∪ | ∪ | The rows in each of the bags | +1 | |

Intersection | ∩ | ∩ | ∩ | The rows that are in both of the bags | +1 | |

Difference | – | – | – | The rows that are in the first bag but not in the second | +1 | |

Partition | ψ | ψ | ψ | Group by, distinct, order by | The columns to be used for partitioning |

In Firefox, I found that I had to magnify some of the symbols to make them readable. The magnification I used is shown in the last column above. For example, the unmagnified full outer join is ⟗ but if you write <font size='+4'>⟗</font> then it looks like this: ⟗. The required magnifications are different for IE and google-chrome.

The following table uses image files instead of unicode characters: